Eleven minutes ago, 80% of the children in a hall were boys. 29 children left the hall. As a result, the number of boys decreased by 40% and the number of girls decreased by 90%. How many children are in the hall at first?
| |
Boys |
Girls |
Total |
| Before |
5 u |
1 u |
6 u |
| Change |
- 2 u |
- 0.9 u |
- 2.9 u |
| After |
3 u |
0.1 u |
3.1 u |
80% =
80100 =
45Number of boys who left the hall
= 40% x 5 u
=
40100 x 5 u
= 2 u
Number of girls who left the hall
= 90% x 1 u
=
90100 x 1 u
= 0.9 u
Total number of children who left the hall
= 2 u + 0.9 u
= 2.9 u
2.9 u = 29
1 u = 29 ÷ 2.9 = 10
Number of children in the hall at first
= 5 u + 1 u
= 6 u
= 6 x 10
= 60
Answer(s): 60
