Two minutes ago, 80% of the pupils in a school field were girls. 13 pupils left the school field. As a result, the number of girls decreased by 40% and the number of boys decreased by 60%. How many pupils are in the school field at first?
| |
Girls |
Boys |
Total |
| Before |
5 u |
1 u |
6 u |
| Change |
- 2 u |
- 0.6 u |
- 2.6 u |
| After |
3 u |
0.4 u |
3.4 u |
80% =
80100 =
45Number of girls who left the school field
= 40% x 5 u
=
40100 x 5 u
= 2 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
= 2 u + 0.6 u
= 2.6 u
2.6 u = 13
1 u = 13 ÷ 2.6 = 5
Number of pupils in the school field at first
= 5 u + 1 u
= 6 u
= 6 x 5
= 30
Answer(s): 30
