Eighteen minutes ago, 75% of the children in a hall were girls. 38 children left the hall. As a result, the number of girls decreased by 25% and the number of boys decreased by 90%. How many children are in the hall at first?
| |
Girls |
Boys |
Total |
| Before |
4 u |
1 u |
5 u |
| Change |
- 1 u |
- 0.9 u |
- 1.9 u |
| After |
3 u |
0.1 u |
3.1 u |
75% =
75100 =
34Number of girls who left the hall
= 25% x 4 u
=
25100 x 4 u
= 1 u
Number of boys who left the hall
= 90% x 1 u
=
90100 x 1 u
= 0.9 u
Total number of children who left the hall
= 1 u + 0.9 u
= 1.9 u
1.9 u = 38
1 u = 38 ÷ 1.9 = 20
Number of children in the hall at first
= 4 u + 1 u
= 5 u
= 5 x 20
= 100
Answer(s): 100
