Twenty minutes ago, 75% of the pupils in a school field were girls. 8 pupils left the school field. As a result, the number of girls decreased by 25% and the number of boys decreased by 60%. How many pupils are in the school field at first?
| |
Girls |
Boys |
Total |
| Before |
4 u |
1 u |
5 u |
| Change |
- 1 u |
- 0.6 u |
- 1.6 u |
| After |
3 u |
0.4 u |
3.4 u |
75% =
75100 =
34Number of girls who left the school field
= 25% x 4 u
=
25100 x 4 u
= 1 u
Number of boys who left the school field
= 60% x 1 u
=
60100 x 1 u
= 0.6 u
Total number of pupils who left the school field
= 1 u + 0.6 u
= 1.6 u
1.6 u = 8
1 u = 8 ÷ 1.6 = 5
Number of pupils in the school field at first
= 4 u + 1 u
= 5 u
= 5 x 5
= 25
Answer(s): 25
