Seventeen minutes ago, 70% of the pupils in a school field were boys. 41 pupils left the school field. As a result, the number of boys decreased by 20% and the number of girls decreased by 70%. How many pupils are in the school field at first?
| |
Boys |
Girls |
Total |
| Before |
10 u |
3 u |
13 u |
| Change |
- 2 u |
- 2.1 u |
- 4.1 u |
| After |
8 u |
0.9 u |
8.9 u |
70% =
70100 =
710Number of boys who left the school field
= 20% x 10 u
=
20100 x 10 u
= 2 u
Number of girls who left the school field
= 70% x 3 u
=
70100 x 3 u
= 2.1 u
Total number of pupils who left the school field
= 2 u + 2.1 u
= 4.1 u
4.1 u = 41
1 u = 41 ÷ 4.1 = 10
Number of pupils in the school field at first
= 10 u + 3 u
= 13 u
= 13 x 10
= 130
Answer(s): 130
