Seven minutes ago, 60% of the children in a hall were girls. 5 children left the hall. As a result, the number of girls decreased by 20% and the number of boys decreased by 75%. How many children are in the hall at first?
| |
Girls |
Boys |
Total |
| Before |
5 u |
2 u |
7 u |
| Change |
- 1 u |
- 1.5 u |
- 2.5 u |
| After |
4 u |
0.5 u |
4.5 u |
60% =
60100 =
35Number of girls who left the hall
= 20% x 5 u
=
20100 x 5 u
= 1 u
Number of boys who left the hall
= 75% x 2 u
=
75100 x 2 u
= 1.5 u
Total number of children who left the hall
= 1 u + 1.5 u
= 2.5 u
2.5 u = 5
1 u = 5 ÷ 2.5 = 2
Number of children in the hall at first
= 5 u + 2 u
= 7 u
= 7 x 2
= 14
Answer(s): 14
