Solution:
We need to use 90 Egyptian scores: 1/2, 1/3, 1/4, …, 1, 1/9 1, and select 10 from them.
So I guess, if we can find a number and use it as the denominator, and at the same time, we can divide this number by its different factors (at least 10), and the sum of different factors is exactly equal to the reciprocal of this denominator, the problem will be solved.
So I want to construct a common multiple of 2,3,4,5,6,7,8,9, which is (2 3) * (3 2) * 5 * 7 = 8 * 9 * 5 * 7.
This number is too big to be used as a denominator.
It is observed that (2 3) * (3 2) = 8 * 9 = 72, which can be used as the common denominator of the next ten fractions.
Careful observation of (2 3) * (3 2) has a factor of 3+2+3*2+ 1= 12, namely:
(2, 4, 8) (3, 9) (6,18,12, 36, 24, 36, 72) (1).
Precautions:
The factor 72 in the first bracket is composed of a single factor 2, namely 2 1, 2 2, 2 3.
The factor 72 in the second bracket is composed of a single factor 3, which is 3 1 and 3 2 respectively.
The factor 72 in the third bracket consists of factor 2 and factor 3, which are 20% products of 2, 4, 8 and 3, 9 respectively.
[The fourth bracket is any number of factors = 1.
Arrange the above factors from small to large, namely 1, 2, 3, 4, 6, 8, 9, 12, 18.24, 36, 72. Because 72/72= 1 is not actually a fraction, this factor is removed.
The remaining problem is how to choose the number 1, 2, 3, 4, 6, 8, 9, 12, 18.24, 36 * * *1and make the result equal to 75430/by adding a symbol.
In EXCEL, select the above-mentioned 10 factors, input them one by one, arrange them in a column, sum them up, and then make the result equal to 72 by "only adjusting the symbol". I got at least the following three sets of results.
A: (-2, 3, 4, -6, -8, -9,-12, 18, -24, -36).
B: (2, 3, -4, -6, 8, -9, 12,-18, -24, -36)
C: (- 1，-2，3，-4，-6，-8，- 12， 18，-24，-36)
So that we can be separated.
Answer: (-2+3+4–6–8–9–12+18–24-36)/72 =-72/72 =-1
b:(2+3–4–6+8–9+ 12– 18–24-36)/72 =-72/72 =- 1
C: (- 1，-2，3，-4，-6，-8，- 12， 18，-24，-36)/72= -72/72 = - 1
Simplify the one on the left to get:
A: (-2+3+4–6–8–9–12+18–24-36)/72
= -2/72 + 3/72 + 4/72 – 6/72 – 8/72 – 9/72 – 12/72 + 18/72 – 24/72 – 36/72
= - 1/36 + 1/24 + 1/ 18 – 1/ 12 – 1/9 – 1/8 – 1/6 + 1/4 – 1/3 – 1/2
b:(2+3–4–6+8–9+ 12– 18–24-36)/72
=2/72 + 3/72 – 4/72 –6/72 + 8/72 – 9/72 + 12/72 – 18/72 – 24/72 –36/72
= 1/36 + 1/24 – 1/ 18 – 1/ 12 + 1/9 – 1/8 + 1/6 – 1/4 – 1/3 – 1/2
c:(- 1–2+3-4-6-8– 12+ 18-24-36)/72
= - 1/72 – 2/72 + 3/72 – 4/72 – 6/72 – 8/72 – 12/72 + 18/72 – 24/72 –36/72
= - 1/72 – 1/36 + 1/24 – 1/ 18 – 1/ 12 – 1/9 – 1/6 + 1/4 – 1/3 – 1/2
2. There are four different numbers between1000 and 9999, and the difference between single digits and thousands is 2. How many such integers are there? (list)
Solutions: 840 kinds
The following are all 840 numbers.
1023 1043 1053 1063 1073 1083 1093 1203
1243 1253 1263 1273 1283 1293 1403 1423
1453 1463 1473 1483 1493 1503 1523 1543
1563 1573 1583 1593 1603 1623 1643 1653
1673 1683 1693 1703 1723 1743 1753 1763
1783 1793 1803 1823 1843 1853 1863 1873
1893 1903 1923 1943 1953 1963 1973 1983
20 14 2034 2054 2064 2074 2084 2094 2 104
2 130 2 134 2 140 2 150 2 154 2 160 2 164 2 170
2 174 2 180 2 184 2 190 2 194 2304 23 10 23 14
2340 2350 2354 2360 2364 2370 2374 2380
2384 2390 2394 24 10 2430 2450 2460 2470
2480 2490 2504 25 10 25 14 2530 2534 2540
2560 2564 2570 2574 2580 2584 2590 2594
2604 26 10 26 14 2630 2634 2640 2650 2654
2670 2674 2680 2684 2690 2694 2704 27 10
27 14 2730 2734 2740 2750 2754 2760 2764
2780 2784 2790 2794 2804 28 10 28 14 2830
2834 2840 2850 2854 2860 2864 2870 2874
2890 2894 2904 29 10 29 14 2930 2934 2940
2950 2954 2960 2964 2970 2974 2980 2984
30 15 302 1 3025 304 1 3045 305 1 306 1 3065
307 1 3075 308 1 3085 309 1 3095 3 105 3 125
3 145 3 165 3 175 3 185 3 195 320 1 3205 32 15
324 1 3245 325 1 326 1 3265 327 1 3275 328 1
3285 329 1 3295 340 1 3405 34 15 342 1 3425
345 1 346 1 3465 347 1 3475 348 1 3485 349 1
3495 350 1 352 1 354 1 356 1 357 1 358 1 359 1
360 1 3605 36 15 362 1 3625 364 1 3645 365 1
367 1 3675 368 1 3685 369 1 3695 370 1 3705
37 15 372 1 3725 374 1 3745 375 1 376 1 3765
378 1 3785 379 1 3795 380 1 3805 38 15 382 1
3825 384 1 3845 385 1 386 1 3865 387 1 3875
389 1 3895 390 1 3905 39 15 392 1 3925 394 1
3945 395 1 396 1 3965 397 1 3975 398 1 3985
40 12 40 16 4026 4032 4036 4052 4056 4062
4072 4076 4082 4086 4092 4096 4 102 4 106
4 126 4 132 4 136 4 152 4 156 4 162 4 172 4 176
4 182 4 186 4 192 4 196 4206 42 16 4236 4256
4276 4286 4296 4302 4306 43 12 43 16 4326
4352 4356 4362 4372 4376 4382 4386 4392
4396 4502 4506 45 12 45 16 4526 4532 4536
4562 4572 4576 4582 4586 4592 4596 4602
46 12 4632 4652 4672 4682 4692 4702 4706
47 12 47 16 4726 4732 4736 4752 4756 4762
4782 4786 4792 4796 4802 4806 48 12 48 16
4826 4832 4836 4852 4856 4862 4872 4876
4892 4896 4902 4906 49 12 49 16 4926 4932
4936 4952 4956 4962 4972 4976 4982 4986
50 13 50 17 5023 5027 5037 5043 5047 5063
5067 5073 5083 5087 5093 5097 5 103 5 107
5 123 5 127 5 137 5 143 5 147 5 163 5 167 5 173
5 183 5 187 5 193 5 197 5203 5207 52 13 52 17
5237 5243 5247 5263 5267 5273 5283 5287
5293 5297 5307 53 17 5327 5347 5367 5387
5397 5403 5407 54 13 54 17 5423 5427 5437
5463 5467 5473 5483 5487 5493 5497 5603
5607 56 13 56 17 5623 5627 5637 5643 5647
5673 5683 5687 5693 5697 5703 57 13 5723
5743 5763 5783 5793 5803 5807 58 13 58 17
5823 5827 5837 5843 5847 5863 5867 5873
5893 5897 5903 5907 59 13 59 17 5923 5927
5937 5943 5947 5963 5967 5973 5983 5987
60 14 60 18 6024 6028 6034 6038 6048 6054
6058 6074 6078 6084 6094 6098 6 104 6 108
6 124 6 128 6 134 6 138 6 148 6 154 6 158 6 174
6 178 6 184 6 194 6 198 6204 6208 62 14 62 18
6234 6238 6248 6254 6258 6274 6278 6284
6294 6298 6304 6308 63 14 63 18 6324 6328
6348 6354 6358 6374 6378 6384 6394 6398
6408 64 18 6428 6438 6458 6478 6498 6504
6508 65 14 65 18 6524 6528 6534 6538 6548
6574 6578 6584 6594 6598 6704 6708 67 14
67 18 6724 6728 6734 6738 6748 6754 6758
6784 6794 6798 6804 68 14 6824 6834 6854
6874 6894 6904 6908 69 14 69 18 6924 6928
6934 6938 6948 6954 6958 6974 6978 6984
70 15 70 19 7025 7029 7035 7039 7045 7049
7059 7065 7069 7085 7089 7095 7 105 7 109
7 125 7 129 7 135 7 139 7 145 7 149 7 159 7 165
7 169 7 185 7 189 7 195 7205 7209 72 15 72 19
7235 7239 7245 7249 7259 7265 7269 7285
7289 7295 7305 7309 73 15 73 19 7325 7329
7345 7349 7359 7365 7369 7385 7389 7395
7405 7409 74 15 74 19 7425 7429 7435 7439
7459 7465 7469 7485 7489 7495 7509 75 19
7529 7539 7549 7569 7589 7605 7609 76 15
76 19 7625 7629 7635 7639 7645 7649 7659
7685 7689 7695 7805 7809 78 15 78 19 7825
7829 7835 7839 7845 7849 7859 7865 7869
7895 7905 79 15 7925 7935 7945 7965 7985
80 16 8026 8036 8046 8056 8076 8096 8 106
8 126 8 136 8 146 8 156 8 176 8 196 8206 82 16
8236 8246 8256 8276 8296 8306 83 16 8326
8346 8356 8376 8396 8406 84 16 8426 8436
8456 8476 8496 8506 85 16 8526 8536 8546
8576 8596 8706 87 16 8726 8736 8746 8756
8796 8906 89 16 8926 8936 8946 8956 8976
90 17 9027 9037 9047 9057 9067 9087 9 107
9 127 9 137 9 147 9 157 9 167 9 187 9207 92 17
9237 9247 9257 9267 9287 9307 93 17 9327
9347 9357 9367 9387 9407 94 17 9427 9437
9457 9467 9487 9507 95 17 9527 9537 9547
9567 9587 9607 96 17 9627 9637 9647 9657
9687 9807 98 17 9827 9837 9847 9857 9867
3. There is a chess piece (less than 100 pieces). Xiaoming took out more than half of all the chess pieces for the first time, more than half of the remaining chess pieces for the second time, and more than half of the remaining chess pieces for the third time ... Finally, 1 piece remains in the fertilized egg. So, how many Go players are there in this zygote at most?
Solution:
{[( 1+ 1)X2+ 1]X2+ 1 } X2 = 22
Take more than half for the first time, that is, 12, leaving10;
Take more than half a second, that is, 6, leaving 4;
The third time, I took more than half of one, that is, three, and finally left 1.
4. The sum of the ages of Party A, Party B, Party C and Party D is 64 years old, and that of Party B, Party C and Party D is 36 years old. The total age of Party A and Party D is twice that of Party B and Party D. What is the total age of the four of them?
Solution:1+1) * 2 = 42 * 4+1= 9.
9 * 2+1=1919 * 2+1= 39 so =79.
39 * 2+ 1 = 79 79 * 2+ 1 & gt； 100
5. There are two trains, one of which is102m long and runs 20m per second; The length of the train is120m, and it runs at the speed of17m per second. Two cars are driving in the same direction. How many seconds does it take from the first train to catch up with the second train to the departure of the two cars?
Solution: This problem is the catch-up problem of "two trains". Here "catching up" means that the head of the first train catches up with the tail of the second train, and "leaving" means that the tail of the first train leaves the head of the second train. Draw a line segment as follows: Let it take x seconds from the first train catching up with the second train to the departure of the two trains, and the equation is: 102+ 128.
6. Someone walks at a speed of 2 meters per second. A train came behind, which took 10 seconds longer than him. As we all know, this train is 90 meters long. Find the speed of the train.
Solution: .2. Draw a line segment as follows: the first 90 meters end point 10x, let the train speed be x meters per second, and the train equation is10x = 90+2×10x =11.
7. It is known that the price of the table is 10 times that of the chair, and the table is 288 yuan more expensive than the chair. How much is a table and a chair?
Solution: According to the known conditions, a table is 288 yuan more than a chair, which is exactly (10- 1) times the price of a chair, so the price of a chair can be obtained. According to the price of chairs, we can get the price of a table. Price of a chair: 288÷( 10- 1)=32 yuan; price of a table: 32× 10=320 yuan.
8.2, 2.3 boxes of apples weigh 45 kilograms. A box of pears is 5 kilograms heavier than a box of apples. How much do three boxes of pears weigh?
Solution: You can first find out how much three boxes of pears weigh than three boxes of apples, and add the weight of three boxes of apples, which is the weight of three boxes of pears. 45+5×3 =45+ 15 =60 (kg)
9.3. Party A and Party B walked across two places at the same time. Four hours later, they met four kilometers from the midpoint. A is faster than B. How many kilometers is A faster than B per hour?
Solution: According to meeting at a distance of 4 kilometers from the midpoint and A's speed is faster than B's, we can know that A walks 4×2 kilometers more than B, and it takes 4 hours to meet. You can work out how many kilometers A is faster than B per hour. 4×2÷4 =8÷4 =2 (km)
9. The school bought 6 tables and 5 chairs and paid 455 yuan. As we all know, every table is more expensive than every chair. 30 yuan, what's the unit price of each desk and chair? 10. A train and a local train leave from Party A and Party B respectively at the same time. The express train is 75 kilometers per hour and the local train is 65 kilometers per hour. When we met, the express train traveled 40 kilometers more than the local train. How many kilometers is it between Party A and Party B? 1 1. A glass factory consigned 250 boxes of glass, and the freight for each box was agreed in the contract in 20 yuan. If a box is damaged, it will not only pay the freight, but also compensate 100 yuan. At the time of settlement after delivery, * * * pays the freight of 4,400 yuan. How many cases of glass are damaged in the consignment? 12. the first and second squadrons of grade five are going for a spring outing 20 kilometers away from the school. The first squadron walks 4 kilometers per hour, and the second squadron rides bicycles, traveling every hour 12 kilometers. The first squadron will leave in two hours, and the second squadron will leave again. How many hours will it take the second squadron to catch up with the first squadron? 13. A pile of coal shipped from the factory will burn 1500 kg a day, one day ahead of schedule. If you burn 1000 kg a day, you will burn one more day than planned. How many kilograms is this pile of coal? 14. Mom sent Xiaohong to the store to buy five pencils and eight exercise books, and gave Xiaohong 3.8 yuan money according to the price. As a result, Xiaohong bought 8 pencils and 5 exercise books and got back 0.45 yuan. How much is a pencil? 15. The school organized a visit abroad, in which 360 teachers and students participated. One bus carries more passengers than one truck 10, and six buses and eight trucks carry the same number of people. How many trucks do you need? How many buses do you need to take? 16. A road construction team undertook the task of building roads. It was originally planned to repair 720 meters a day, but it was actually repaired 80 meters more than the original plan, so that the actual repair difference 1200 meters can be completed three days in advance. What is the total length of this highway? 17. A shoe factory produced 1800 pairs of shoes, which were packed in 12 cartons and 4 wooden cases respectively. If there are as many shoes in 3 cartons as in 2 wooden boxes. How many pairs of shoes are there in each carton and wooden box? 18. A batch of sand and cement was brought into a construction site, with twice as many bags of sand as cement. Use 30 bags of cement and 40 bags of sand every day. After a few days, all the cement was used up, leaving 120 bags of sand. How many bags of sand and cement are there? 19. The school bought five thermos bottles and 10 teacups, and * * * used 90 yuan money. The price of each thermos is four times that of each teacup. How much is each thermos and teacup? 20. The sum of two numbers is 572, and one of them is 0 of several digits. After removing 0, it is the same as the second addend. What are these two numbers? 2 1. Weight of a barrel of oil16kg. After half use, the barrel weighs 9 kilograms. How many kilometers does this bucket weigh? 22. Weight of a barrel of oil 10 kg. After pouring out half, the barrel weighs 5.5 kilograms. How many kilograms of oil are there? 23. Use a bucket of water, double the water, and the weight of the bucket is 10 kg. If the water is increased to 5 times, the weight of the bucket is 22 kilograms. How many kilograms of water are there in the bucket? 24. Xiaohong and Xiaohua have 36 story books. If Xiaohong gives Xiaohua five books, they have the same number of story books. How many books do Xiaohong and Xiaohua have? 25. There are five barrels of oil of the same weight. If 15kg is taken out of each barrel, the weight of the remaining oil in five barrels is exactly equal to the weight of the original two barrels. How much does a barrel of oil weigh? 26. It takes 9 minutes to saw a piece of wood into 3 sections, so how many points does it take to saw this piece of wood into 5 sections at the same speed? 27. In a workshop, there are 35 fewer female workers than male workers. 17 after the transfer of male and female employees, the number of male employees is twice that of female employees. How many people are there? How many women workers are there? 28. Li Qiang rides a bike from place A to place B at a speed of 12km, and it takes five hours to get there. When returning from B to A, it took 1 hour more because of the headwind. How many kilometers does he drive per hour on average? 29. Party A and Party B walk at the same time from two places 18km apart, with Party A walking 5km per hour and Party B walking 4km per hour. If A starts with a dog and A at the same time, the dog runs to B at a speed of 8 kilometers per hour. When it meets B, it immediately runs back to A, and when it meets A, it flies back. How many kilometers did the dog run when they met? 10, think: according to the known speed of two cars, find the speed difference, according to the speed difference of two cars and the distance between the express train and the local train, find the travel time of two cars, and then find the distance between Party A and Party B. Solution: (7+65) × [40 ÷ (75-65)] =140. 1 1. Think about it: According to the 250 boxes of glass that are known to be consigned, the total freight payable can be calculated according to each box of 20 yuan. According to the damage of each box, not only do you not pay the freight, but you also pay compensation of 100 yuan. The difference between the known payable amount and the actual paid amount is several yuan (100+20), that is, several boxes are damaged. Solution: (20× 250-4400) ÷ (10+20) = 600 ÷120 = 5 (boxes) A: Five boxes are damaged. 12, I think: because the first squadron started 2 hours 4×2 kilometers earlier than the second squadron, and the second squadron traveled (12-4) kilometers more than the first squadron every hour, we can find the time when the second squadron caught up with the first squadron. Solution: 4× 2 ÷ (1 2-4) = 4× 2 ÷ 8 =1(hour) Answer: The second squadron can catch up with the first squadron within1hour. 13, I think: according to the known conditions, the difference between the total amount of coal burned before and after is (1500+ 1000) kg, which is caused by the difference of (1500- 1000) kg per day. From this, we can find out the number of days we planned to burn, and then find out this. Solution: The original planned days of burning coal: (1500+1000) ÷ (1500-1000) = 2500 ÷ 500 = 5 (days) Weight of this pile of coal:/. 14, I think: the total number of pencils and notebooks that Xiaohong intends to buy is equal to the total number of pencils and notebooks actually bought. The change of 0.45 yuan means that (8-5) pencils are counted as (8-5) exercise books, with a difference of 0.45 yuan. From this, we can find out how much the unit price of exercise books is more expensive than pencils. Judging from the total amount of money, eight exercise books are more expensive than eight pencils, leaving (5+8) pencils. Then you can work out the price of each pencil. Solution: The amount of money that each exercise book is more expensive than each pencil: 0.45÷(8-5)=0.45÷3=0. 15 (yuan) The amount of money that eight exercise books are more expensive than eight pencils: 0. 15× 8 =/kloc-0. Think about it: According to the passenger car is overloaded with freight cars 10, we can find out the number of people who are overloaded with six passenger cars than six freight cars, that is, the number of people on multi-purpose (8-6) freight cars, and then find out how many people are on each freight car and how many people are on each bus. Solution: number of freight cars: 360 ÷ [10× 6 ÷ (8-6)] = 360 ÷ [10× 6 ÷ 2] = 360 ÷ 30 =12. Solution: Repair days: (720× 3-1200) ÷ 80 = 960 ÷ 80 =12 (days) Total highway length: (720+80 )×12+/kloc-. 17, I think: according to the known conditions, we can find the number of 12 cartons converted into wooden cases. First, we can work out how many pairs are packed in each carton, and then we can work out how many pairs are packed in each carton. Solution: 12 cartons are equivalent to the number of wooden cases: 2× (12 ÷ 3) = 2× 4 = 8 (pieces) Even number of shoes in a wooden case:1800 ÷ (8+4) =1 Think about it: according to the known conditions, we can know that 30 bags of cement and 30×2 bags of sand can be used up at the same time every day. But now only 40 bags of sand are used every day, and even fewer bags (30×2-40) are used, so the total is 120 bags of sand. Therefore, according to the number of less sand bags used in 120 bag, the service days can be calculated. Then you can get the total number of bags of sand and cement. Solution: Days when cement is used up:120 ÷ (30× 2-40) =120 ÷ 20 = 6 (days) Total number of cement bags: 30×6= 180 (bags) Total number of sand bags: 60. 19: If the price of each thermos is four times that of each teacup, the price of five thermos can be converted into the price of 20 teacups. In this way, the 90 yuan money for five thermos bottles and 10 teacups can be regarded as the money for 30 teacups. Solution: Price of each teacup: 90÷(4×5+ 10)=3 yuan; Price of each thermos: 3×4= 12 yuan; Answer:1Every thermos in 2 yuan and every teacup in 3 yuan. 20. Think about it: it is known that an addend is 0 of several digits. If you remove 0, it will be the same as the second addend. Knowing that the first addend is 10 times of the second addend, the sum of the two addends is 572 times of the second addend. Solution: The first addend: 572÷( 10+ 1)=52 The second addend: 52× 10=520 A: These two addends are 52 and 520 respectively. 2 1, I think: according to the known conditions, the difference between 16 kg and 9 kg is exactly the weight of half a barrel of oil. 9 kg is the weight of half a barrel of oil and barrel, and the weight of half a barrel of oil is the weight of barrel. Solution: 9-( 16-9) =9-7 =2 (kg) A: The barrel weighs 2 kg. 22. Think about it: According to the known conditions, the difference between 10 kg and 5.5 kg is exactly the weight of half a barrel of oil, and then multiplied by 2 is the weight of the original oil. Solution: (10-5.5)×2=9 (kg) Answer: There are 9 kg of oil. 23. Think about it: According to the known conditions, the original water in the barrel is (5-2) times exactly (22- 10) kg, from which the weight of the original water in the barrel can be calculated. Solution: (22-10) ÷ (5-2) =12 ÷ 3 = 4 (kg) Answer: The original water in the barrel is 4 kg. 24. Thinking: From the condition that "Xiao Hong gives Xiao Hua five books, and the number of story books for both of them is equal", we can know that Xiao Hong has (5×2) more books than Xiao Hua, and the number of books that Xiao Hong has more than Xiao Hua is subtracted from * *, and the remaining number is exactly twice that of Xiao Hua. Solution: The number of books owned by Xiaohua is (36-5×2)÷2= 13 (books). The number of books owned by Xiaohong is 13+5×2=23. Answer: Xiaohong has 23 books and Xiaohua 13 books. 25. Think: According to the known conditions, take out (15×5) kg of 5 barrels of oil. Since the weight of the remaining oil is exactly equal to the original 2 barrels of oil, it can be deduced that the weight of (5-2) barrels of oil is (15×5) kg. Solution: 15×5÷(5-2)=25 (kg) Answer: The original weight of oil per barrel is 25 kg. 26. Thinking: Saw a piece of wood into three sections and only saw (3- 1) kerfs, so that the time required for sawing each kerf can be calculated, and then the time required for sawing into five sections can be calculated. Solution: 9 ÷ (3-1) × (5-1) = 18 (minutes) A: It takes18 minutes to saw into five sections. 27. Thinking: There are fewer female workers than male workers. 17 After the male and female workers changed jobs, there were still 35 fewer female workers than male workers. At this time, the number of male employees is twice that of female employees, which means that 35 employees are (2- 1) times that of female employees. In this way, the number of female workers can be found out, and then the original number of male and female workers can be found out separately. Solution: 35÷(2- 1)=35 (person) Former female worker: 35+ 17=52 (person) Former male worker: 52+35=87 (person) A: There are 87 male workers and 52 female workers. 28. Think about it: the distance between the two places can be calculated by driving12km per hour and arriving in 5 hours, that is, the distance traveled when returning. It takes 1 hour from 5 hours to return, and the time required for return can be calculated. Solution:12× 5 ÷ (5+1) =10 (km) Answer: On the return trip, the average hourly line 10 km. 29. I think: from the meaning of the question, the time when the dog runs is just the time when the two meet, and I know the speed of the dog, then we can know how many kilometers the dog has run. Solution: 18÷(5+4)=2 (hours) 8×2= 16 (kilometers) A: The dog ran away 16 kilometers. I'm exhausted. I need to mention it again.