There were 56 students in the mathematics interest group of a school, among whom, girls accounted for 85%, and then transferred to some boys. At this time, the ratio of the number of girls to the number of boys was 7; 5. How many boys were transferred later

There were 56 students in the mathematics interest group of a school, among whom, girls accounted for 85%, and then transferred to some boys. At this time, the ratio of the number of girls to the number of boys was 7; 5. How many boys were transferred later

4 people

Pool volume: 14 * 2.8 M3
Volume of injected water per second: pi * 0.5 ^ 2 * 18 = 14.14
Time: 50.4 / 14.14 = 3.57 (seconds)

Pi * 0.5 ^ 2 is the area of circle and pi * 0.5 ^ 2 * 18 is the volume of cylinder
Cylinder volume = circle area * height

There are three people in the family. My father is three years older than my mother. Now the total age of the family is 80 years old. Ten years ago, the total age of the whole family was 51 years old. My daughter is now 80 years old______ I'm 40 years old

3 × 10 = 30 (years old) & nbsp; 80-51 = 29 (years old) & nbsp; & nbsp; 30-29 = 1 (years old) so ten years ago, my daughter was not born, nine years ago, so I am nine years old