Four minutes ago, 60% of the pupils in a school field were boys. 10 pupils left the school field. As a result, the number of boys decreased by 20% and the number of girls decreased by 75%. How many pupils are in the school field at first?
| |
Boys |
Girls |
Total |
| Before |
5 u |
2 u |
7 u |
| Change |
- 1 u |
- 1.5 u |
- 2.5 u |
| After |
4 u |
0.5 u |
4.5 u |
60% =
60100 =
35Number of boys who left the school field
= 20% x 5 u
=
20100 x 5 u
= 1 u
Number of girls who left the school field
= 75% x 2 u
=
75100 x 2 u
= 1.5 u
Total number of pupils who left the school field
= 1 u + 1.5 u
= 2.5 u
2.5 u = 10
1 u = 10 ÷ 2.5 = 4
Number of pupils in the school field at first
= 5 u + 2 u
= 7 u
= 7 x 4
= 28
Answer(s): 28
