Three minutes ago, 70% of the pupils in a parade square were boys. 57 pupils left the parade square. As a result, the number of boys decreased by 30% and the number of girls decreased by 90%. How many pupils are in the parade square at first?
| |
Boys |
Girls |
Total |
| Before |
10 u |
3 u |
13 u |
| Change |
- 3 u |
- 2.7 u |
- 5.7 u |
| After |
7 u |
0.3 u |
7.3 u |
70% =
70100 =
710Number of boys who left the parade square
= 30% x 10 u
=
30100 x 10 u
= 3 u
Number of girls who left the parade square
= 90% x 3 u
=
90100 x 3 u
= 2.7 u
Total number of pupils who left the parade square
= 3 u + 2.7 u
= 5.7 u
5.7 u = 57
1 u = 57 ÷ 5.7 = 10
Number of pupils in the parade square at first
= 10 u + 3 u
= 13 u
= 13 x 10
= 130
Answer(s): 130
