Elementary school math problem 1 1.

1. Let's count the number of female athletes first.

138÷2-7=62

How many male and female athletes are there?

62+ 138=200

A: There are 200 male and female athletes.

2. Divide the valid votes obtained by Beijing by the total valid votes.

Solution: 56÷ 105=56/ 105, rounded to get 8/ 15.

3. Since A goes every six days, B goes every eight days and C goes every nine days, we can know that the days from April 25th to their next visit to the library are the least common multiple of 6, 8 and 9, and the least common multiple is 72, and 72 days is more than two months, so we can work out how many days are left in April, May and June, and finally subtract them from 72.

Solution: 6=2×3, 8=2×2×2, 9=3×3,

So the least common multiple of 6, 8 and 9: 2× 3× 2× 2× 3 = 72;

April, June, abortion, 30 days, May, big month, 3 1 day.

So there are still: April 30-25=5, May 3 1 day, June 30 days.

Remaining: 72-5-3 1-30=6 (days);

That is, the next time I go to the library is July 6;

A: The next time I go to the library is July 6th.

4. Require "how many meters of cloth is used for each pair of trousers", that is, the length of cloth divided by the number of trousers, and the formula is 8÷ 12, and the result can be calculated. This question is about how many meters of cloth each pair of trousers uses, so it is necessary to bring units;

The second question is how much this kind of cloth is used for each pair of trousers, that is, 8 meters is used as the unit "1", and the formula is 1 ÷ 12.

Solution: (1) 8 ÷12 = 2/3 (m);

(2) 1÷ 12= 1/ 12 .

Answer: Each pair of trousers is made of 2/3 meters of cloth, and each pair of trousers is made of112 of this cloth.

5. Find the greatest common factor of the length and width of a rectangle as the side length of a big square, and the greatest common factor of 20 and 16 is 4, so if 4 cm is used as the side length of a big square, the long side can be cut by 5 and the width can be cut by 4, and this problem can be cut by 20.

Solution: The side length of the secant square is the greatest common factor of 20 and 16;

So the side length of a square is 4 cm,

20÷4=5 (column),

16÷4=4 (line),

5×4=20 (pieces),

So the answer is: 20.

6. Because the distance between the two cars is 36 kilometers when they meet, the second car is (36×2)72 meters longer than the first car (distance difference). Divide the distance difference of 72 meters by the speed difference of (54-48)6 meters, which is equal to the meeting time. Then divide the speed sum of (54+48)102m by the meeting time, which is the distance between A and B..

Solution: (48+54)×[(36×2)÷(54-48)],

= 102×[72÷6],

= 102× 12,

= 1224 (km);

A: The distance between A and B is 1224 km.

1. Take the total area of this land as the unit "1" and subtract the percentage of corn and vegetables from the unit "1" to get the percentage of watermelon planting area.

Solution:1-(1/5+1/6),

= 1- 1 1/30,

= 19/30.

A: Watermelon planting area accounts for 19/30 of this land.

2. Solution: The number of girls is the number of boys: 20 ÷ 24 = 5/6;

How many times more boys than girls? ：

24÷20= 1.2

A: The number of girls is 5/6 of that of boys, and the number of boys is 0.2 times that of 65438+ girls.

3. Solution: 3/5+ 1/8+3/5=53/40.

Answer: 53/40 tons of garbage was cleared in grades 5 and 6.

4. Solution: (40-4×2)×(30-4×2)×4,

=(40-8)×(30-8)×4,