The teacher said to Xiaoming, "When I was your age, you were only 3 years old. I was 42 years old when you were my age. " Ask Mr. Li's age
We assume that the age difference will never change, and I really think of it as "1".
When the teacher was as old as Xiao Ming, Xiao Ming was 3 years old. When Xiao Ming was the same age as his teacher, the teacher was 42 years old, and 42-3=39 years old. There are three age differences at 39. When Xiaoming was 3 years old, he was one year behind his teacher. When the teacher is 42 years old, there are two age differences, so each difference is 39/3= 13 years old.
Xiao Ming is 42- 13*2= 16.
Teacher 42- 16=29 years old.
Let me ask you a few questions: 1 There is a cinema, and * * * has 200 seats. Among them, there is one ordinary seat in 25 yuan and one deluxe seat in 45 yuan. All the tickets are sold out, and the price of ordinary seats is higher than that of deluxe seats 10 10 yuan. How many seats are there?
Answer: Assuming that all 200 seats are ordinary seats, the fare of ordinary seats is 200 * 25 = 5,000 yuan, and the luxury seat is 0 yuan, and the fare of ordinary seats is 5,000 yuan more than that of luxury seats.
Now, if the ordinary seats are replaced by deluxe seats, that is, 199 ordinary seats and 1 deluxe seats, the fares are 4,075 yuan and 45 yuan respectively, and the ordinary seats are 4,030 yuan more than the deluxe seats. Compared with the original 5,000 yuan, the surplus is less than that of 70 yuan. In this way, every time one is replaced, the redundant part will be less 70 yuan.
In fact, the fare of ordinary seats is more than that of deluxe seats 10 10 yuan, 5000-10/kloc-0 = 3990 yuan. How many seats should be replaced? Namely: 3990/70 = 57.
So the ordinary seat is: 200-57 = 143.
Deluxe seats: 57 seats
A and B are 69 years old this year. Three years ago, A was three years older than B. How old are A and B this year?
A: Three years ago, A was three years older than B. The age gap between them will not change.
A is still three years older than B this year.
This year,
A (69+3)/2=36 years old
B 36-3=33 Yes
3. Divide 12 by the sum of three different natural numbers not greater than 7. Please list how many points there are.
There are some watermelons in the shop. Half of them were sold on the first day, the remaining half on the second day and 30 on the third day. How many watermelons are there?
Some students plant trees in spring. If everyone plants 4 trees, there are 10 trees left. If everyone plants 6 trees, there will be 20 fewer trees. How many people plant trees? How many trees have been planted?
Four years ago, my father was five times as old as Xiao Ming. This year, the sum of the ages of father and son is 56. How old is Xiaoming?
6. Son 12 years old, father 36 years old. How many years later, the father is exactly twice the age of his son?
7. A, B and C each have several story books. If A gives B 5 books, B gives C 10 books and C gives A 15 books, there are now 35 story books for three people. How many copies do they have?
8 Best answer 1, one prize for the first prize, the second prize and the third prize. The bonus of each first prize is twice that of each second prize, and the bonus of each second prize is twice that of each third prize. If there are two first, second and third prizes, then the bonus for each first prize is 308 yuan. If only the first prize 1 person, 2 second prizes and 3 third prizes are awarded, what is the bonus of the first prize?
The first prize is 308 yuan.
308÷2= 154 yuan, second prize 154 yuan.
154÷2=77 yuan, and the third prize is 77 yuan.
(308+154+77) * 2 = 1078 yuan, and the total prize amount is1078 yuan.
First prize =2 times second prize =4 times third prize
So 2 second prizes = 1 first prize, 3 third prizes =3/4 first prizes.
1078 ÷ (1+1+3/4) = 392 yuan, and the first prize is 392 yuan.
Equation:
If the bonus of each first prize is 308 yuan according to the first distribution method, the total amount is (308+154+77) * 2 =1078 yuan. According to another setting method, if the third prize is X yuan, then 2*2x+2*2x+3x= 1078, then x =98.
It can be said that the third prize was 98 yuan, the second prize was 196 yuan, and the first prize was 392 yuan.
2. The charging standard of tap water for residents in a city is: the monthly water consumption of each household does not exceed 4 tons, each ton 1.80 yuan. When it exceeds four tons, it exceeds one ton of 3 yuan. In a certain month, two households paid 26.40 yuan for water, and the water consumption ratio was 5: 3. How much water does each household have to pay?
Solution: The water consumption of household A is 5 tons, and that of household B is 3 tons.
1.8 * 4+3 *(5x-4)+ 1.8 * 4+3 *(3x-4)= 26.4 x = 1.5
5x = 7.5，3x = 4.5。
Then the water fee payable by Party A is1.8 * 4+3 * (7.5-4) = 7.2+10.5 =17.7 (Yuan).
The water fee payable by Party B is1.8 * 4+3 * (4.5-4) = 7.2+1.5 = 8.7 (Yuan).
There are three good friends in a beautiful village: Xiaoming, Xiaogang and Xiaoqiang. They often fish together. Once, they were busy for a long time and caught a lot of fish. I was so tired that I sat under the willow by the river and rested, and soon fell asleep. Xiao Ming woke up and remembered some things at home. He saw Xiao Gang and Xiao Qiang sleeping soundly and didn't wake them up. He divided the fish into three parts, took one and left. Xiao Gang soon woke up and wanted to go home. He also divided the fish into three parts, took one and left. Xiao Qiang didn't wake up until the sun went down. He thought, where did Xiao Ming and Xiao Gang go? It's so late, I have to go home and cut wood. So he divided the fish into three parts and took one for himself. Finally, there are eight fish left.
The next day, they teamed up to go fishing by the river, only to know that the fish sent yesterday was unreasonable. Xiaoming immediately gave the remaining eight fish to Xiaogang No.3 and Xiao Qiang No.5.. Can you figure out how many fish they caught in the past?
Because the last eight fish are two of the three parts of Xiao Qiang's score, Xiao Qiang took 8÷2 fish. Then the fish left by Xiaogang after taking his share is 8÷2×3, accounting for two of Xiaogang's three shares, so the fish taken by Xiaogang is (8 ÷ 2× 3) ÷ 2; We can also know that the fish that Xiaoming took was [(8 ÷ 2× 3) ÷ 2× 3] ÷ 2. So the number of fish caught is [(8 ÷ 2× 3) ÷ 2× 3] ÷ 2× 3 = 27 (strips).
Of course, we can also bring 8 fish from Xiao Qiang on the first day and 5 fish on the second day. We know that everyone takes 8 ÷ 2+5 fish on average, so the number of fish caught is (8 ÷ 2+5) × 3 = 27 (fish).
Once 10, Xiaoming brought a basket of pears from the mountain. He called Xiaogang and Xiao Qiang and said to them, "I'll give you some pears first, and the rest is mine." So, he gave half a yamanashi to Xiaogang, and then added 1 to Xiaogang. Then, he gave the remaining half to Xiao Qiang, added 1 to Xiao Qiang, and finally left five yamanashi for himself.
Xiao Ming, do the math. How many yamanashi are there in this basket?
Then list the formulas:
(5+l)×2+ 1]×2
=[6×2+ 1〕×2
= 26 (pieces)
A: There are 26 yamanashi in a basket.
There are 10 planes parked at the airport. After the first plane takes off, a plane takes off every four minutes. Two minutes after the first plane took off, a plane landed at the airport. After that, a plane landed at the airport every six minutes, and the plane that landed at the airport took off after the original 10 plane, with an interval of four minutes. Q: After the first plane took off, how long did it take before the plane stopped at the airport?
36+24+16+12+8+4+4 =108 (points)
Or for:
4×[( 10-L)+6+4+3+2+L+L]= 108(min)。
12 A, B and C ships * * * carried 9400 cases, with ship A carrying 300 cases more than ship B and ship C carrying 200 cases less than ship B. How many cases do you want each of the three ships to carry?
This problem can be thought of as follows: According to the fact that Ship A has 30O more boxes than Ship B, assuming that Ship A has as many boxes as Ship B, then Ship A will have 300 fewer boxes, so the total number of boxes shipped will be reduced by 300 boxes to (9400-300) boxes.
According to the fact that ship C has 200 boxes less than ship B, assuming that ship C has as many boxes as ship B, then ship C has 200 more boxes than before. Therefore, the total number of cases of Minlang's elegy will increase by 200, becoming (9400-300+200).
After this adjustment, the total number of containers of the three shipping companies is (9400-300+200). According to the hypothesis, this is exactly three times the number of boxes transported by ship B, so we can find out the number of boxes transported.
13 Go to Class 8 of Qianjin Primary School to help farmers pick beans. The weight of picking beans in each shift is 55 kg, 50 kg, 48 kg, 54 kg, 49 kg, 53 kg, 54 kg and 53 kg respectively. How many Jin of beans are picked in each class on average?
"See who is fast." Teacher Liu encouraged.
Ryan quickly raised his hand and replied: "On average, each class picks 52 pounds." Teacher Liu nodded and said, "Can you tell me the calculation method?"
Ryan said: "There is a trick to finding the average, that is, first determine a benchmark number among these numbers. For example, this question is based on 50. Then add up the kilograms of five classes that exceed the reference number and subtract the kilograms of the remaining two classes that are less than the reference number. The number obtained is divided by 8, and the quotient plus the reference number is the average. "
Teacher Liu said happily; "Very well, we can give a name to Ryan's method, which is called' Less and More'. When doing this, you can choose the benchmark number 50 first, and then look at the back from the front. Write addition before the large number and subtraction before the small number, that is:
5+0-2+4-l+3+4+3= 16
16÷8=2
50+2 = 52kg
This is the average weight of each shift. "
Teacher Liu added: "It is a good method to find the average value quickly and with less calculation."
14, Nanjing Yangtze River Bridge * * * is divided into two layers, the upper layer is a highway bridge and the lower layer is a railway bridge. The railway bridge and highway bridge are * * * long11270m, and the railway bridge is 2270m longer than the highway bridge. How long is the highway and railway bridge of Nanjing Yangtze River Bridge?
Solution: Typical sum-difference problem,
Railway bridge = (11270+2270) ÷ 2 = 6770m highway bridge =11270-6770 = 4500m.
There are 15, and there are 180 people in three groups. The sum of the number of people in the first and second groups is 20 more than that in the third group, and the first group is 2 less than that in the second group. Find the number of people in the first group.
Solution: First, consider the first group and the second group as a whole. The sum of them and the third group is 180, with a difference of 20.
Number of three groups = (180-20) ÷ 2 = 80.
One, two, one together is 180-80 = 100 people, and the difference between group one and group two is 2.
One group number = (100-2) ÷ 2 = 49 Two groups number = 100-49 = 5 1.
16, two baskets of apples, basket a is heavier than basket b 19 kg. How many kilograms are taken out of basket A and put into basket B, so that there are 3 kilograms more apples in basket B than in basket B?
Solution: Since the number of apples in Party A's and Party B's baskets is unknown, we can directly set the number, that is, there are 19 kg apples in Party A's basket and 0 kg apples in Party B's basket ... At this time, the sum of Party A and Party B is 19 kg. After the change, the total is still 19 kg. When the difference between basket B and basket A is 3, then basket B = (19+3) ÷ 2 =11kg. Two children line up to do exercises, and the whole class forms two teams, each with 15 people and the distance between the two teams is 15.