Twenty minutes ago, 70% of the pupils in a hall were girls. 108 pupils left the hall. As a result, the number of girls decreased by 30% and the number of boys decreased by 80%. How many pupils are in the hall at first?
| |
Girls |
Boys |
Total |
| Before |
10 u |
3 u |
13 u |
| Change |
- 3 u |
- 2.4 u |
- 5.4 u |
| After |
7 u |
0.6 u |
7.6 u |
70% =
70100 =
710Number of girls who left the hall
= 30% x 10 u
=
30100 x 10 u
= 3 u
Number of boys who left the hall
= 80% x 3 u
=
80100 x 3 u
= 2.4 u
Total number of pupils who left the hall
= 3 u + 2.4 u
= 5.4 u
5.4 u = 108
1 u = 108 ÷ 5.4 = 20
Number of pupils in the hall at first
= 10 u + 3 u
= 13 u
= 13 x 20
= 260
Answer(s): 260
