Kobayashi entered the numbers 1, 2 ..., n into the computer to get the average. When he thought he had finished typing, the computer showed that he had only entered the number (n- 1), with an average of 35 5/7. Assuming that the number (n- 1) is entered correctly, the missing number is (.

Xiaoshengchu Series Comprehensive Simulation Test Paper (1)

First, fill in the blanks:

3. For a two-digit number, after the exchange of ten digits and one digit, the two digits obtained are 27 less than the original number, so there are _ _ _ _ _ _ qualified two digits.

5. The blank part in the figure accounts for _ _ _ _ _ _ _ of the square area.

6.A and B are 2 10 km apart on the same river. If the two ships are opposite, they will meet after 2 hours; If we go in the same direction, A will catch up with B in 14 hour, and the speed of A's ship is _ _ _ _ _.

7. Fill the seven numbers 1 1 to 17 in the diagram to make the sum of three numbers in each row equal.

8. The average weight of Party A, Party B and Party C is 60 kilograms. If the average weight of Party A and Party B is 3 kilograms more than that of Party C, and Party A is 3 kilograms more than that of Party C, then the weight of Party B is _ _ _ _ _ _ _ _.

9. If there is a number, the remainder after dividing by 3 is 2, and the remainder after dividing by 4 is 1, then the remainder after dividing by 12 is _ _ _ _.

10. At present, all seven coins are arranged face up. If you flip six coins at a time, can the tails of seven coins face up (filled or not) after several flips?

Second, answer questions:

1.500g 70% alcohol solution and 300g 50% alcohol solution are mixed. What is the concentration?

2. How many triangles are there in the picture?

3. A four-digit number, the first digit is equal to 0 digits in the number, the second digit represents/kloc-0 digits in the number, the third digit represents 2 digits in the number, and the fourth digit is equal to 3 digits in the number. Find this four-digit number

Answers to Xiaoshengchu Series Comprehensive Simulation Test Paper (1)

First, fill in the blanks:

1.( 1)

3.(6)

Let the original two digits be 10a+b, then after one digit is exchanged with ten digits, the new two digits are 10b+a, and the difference between them is (10a+b)-(10b+a) = 9 (A- b).

4.(99)

5. (Half)

Replace the semicircle on the left in the original picture with the semicircle with the same area on the right half to get the right picture.

6.(60 km/h)

The two ships face each other and meet in two hours. The sum of the two ships' speeds is 210 ÷ 2 =105 (km/h); The two ships sail in the same direction. In 14 hours, A catches up with B, so the speed of A-B is 210 ÷14 =15 (km/h). We can get A:( 105+65438+ from the sum-difference problem.

B: 60- 15=45 (km/h).

7.11+12+14+15+16+17 = 98. 17th generation, it is found that when a= 1 1, 14,17, 98+2a is a multiple of 3.

(1) when a= 1 1, 98+2a= 120, 120÷3=40.

(2) When a =14,98+2a =126, 126÷3=42.

(3) When a =17,98+2a =132, 132÷3=44.

The corresponding solution is shown in the above figure.

8.(6 1)

The average weight of Party A and Party B is 3 kg more than that of Party C, that is, the weight of Party A and Party B is 3×2=6 (kg) more than that of Party C.. It is known that Party A is 3 kg heavier than Party C, Party B is 6-3=3 kg heavier than Party C, and the weight of Party C+average difference = the average weight of three people, so the weight of Party C = 60-(3× 2) ÷.

9.(5)

The smallest integer that meets the conditions is 5. Then the least common multiple of 3 and 4 is accumulated. All the integers 5, 17, 29, 4 1, … that meet this condition are multiples of 12, so the remainder of their division by 12 is equal, that is, they are all equal to 5.

10. (Cannot)

If all seven coins are turned upside down, the total number of times these seven coins are turned over should be the sum of seven odd numbers, but seven coins are turned over six times at a time, so no matter how many times they are turned over, the total number of times is still the sum of several even numbers, so the requirements in the topic cannot be met.

Second, answer questions:

1.(62.5%)

The weight of mixed alcohol solution is 500+300=800 (g), the content of pure alcohol after mixing is 500× 70%+300× 50% = 350+150 = 500 (g), and the concentration of mixed solution is 500 ÷ 800 = 0.60.

2.(44)

(1) first observe the rectangle inside, as shown in figure 1. There are eight smallest triangles and four small triangles. There are four triangles composed of four small triangles, so the innermost rectangle has 16 triangles.

(2) Expand the rectangle inside to Figure 2, and add the expanded part with dotted lines. Among the newly added triangles, there are 8 smallest triangles: there are 4 triangles composed of two small triangles; There are four triangles, which are composed of four small triangles; There are four triangles composed of eight small triangles, so 28 triangles are added. According to (1) and (2), there is a triangle * * *: 16+28=44 (pieces).

3.( 12 10 and 2020)

Starting from the number and position of the number 0 in the four digits, it is found that the highest bit is not 0, so there is at least one number 0. If there are three numbers 0 and the first number is 3, then the last number of these four numbers is non-zero, so the number of digits exceeds four. Therefore, the number of zeros cannot exceed two.

There is only one (1)0, so the first position is 1 and the second position cannot be 0 or 1. If it is 2, there must be another 1. At this time, because there are already 2, the third bit is 1, and the last bit is 0; It is impossible for the second number to be greater than 2.

(2) There are exactly two zeros, the first digit can only be 2, and the third digit cannot be 0, so there are two zeros in the second and fourth digits. Now look at the third place, because the second and fourth places are both 0, so it can't be 1 and 3, and it can't be more than 3, only 2.

4.(0.239)

That is 0.2392 ...