There was an equal number of boys and girls at the school hall. After
29 of the boys and 41 girls left the school hall, there were 21 more boys than girls at the school hall. How many pupils were there at the school hall at first?
| |
Boys |
Girls |
| Before |
9 u |
9 u |
| Change |
- 2 u |
- 41 |
| After |
7 u |
9 u - 41 |
Number of boys in the end
= 9 u - 2 u
= 7 u
If another 21 girls entered the school hall, the number of boys and girls would be the same.
9 u - 41 + 21 = 7 u
9 u - 20 = 7 u
9 u - 7 u = 20
2 u = 20
1 u = 20 ÷ 2 = 10
Number of pupils in the school hall at first
= 18 u
= 18 x 10
= 180
Answer(s): 180
