Six minutes ago, 80% of the pupils in a school field were boys. 28 pupils left the school field. As a result, the number of boys decreased by 40% and the number of girls decreased by 80%. How many pupils are in the school field at first?
| |
Boys |
Girls |
Total |
| Before |
5 u |
1 u |
6 u |
| Change |
- 2 u |
- 0.8 u |
- 2.8 u |
| After |
3 u |
0.2 u |
3.2 u |
80% =
80100 =
45Number of boys who left the school field
= 40% x 5 u
=
40100 x 5 u
= 2 u
Number of girls who left the school field
= 80% x 1 u
=
80100 x 1 u
= 0.8 u
Total number of pupils who left the school field
= 2 u + 0.8 u
= 2.8 u
2.8 u = 28
1 u = 28 ÷ 2.8 = 10
Number of pupils in the school field at first
= 5 u + 1 u
= 6 u
= 6 x 10
= 60
Answer(s): 60
