Two minutes ago, 70% of the children in a canteen were boys. 128 children left the canteen. As a result, the number of boys decreased by 40% and the number of girls decreased by 80%. How many children are in the canteen at first?
| |
Boys |
Girls |
Total |
| Before |
10 u |
3 u |
13 u |
| Change |
- 4 u |
- 2.4 u |
- 6.4 u |
| After |
6 u |
0.6 u |
6.6 u |
70% =
70100 =
710Number of boys who left the canteen
= 40% x 10 u
=
40100 x 10 u
= 4 u
Number of girls who left the canteen
= 80% x 3 u
=
80100 x 3 u
= 2.4 u
Total number of children who left the canteen
= 4 u + 2.4 u
= 6.4 u
6.4 u = 128
1 u = 128 ÷ 6.4 = 20
Number of children in the canteen at first
= 10 u + 3 u
= 13 u
= 13 x 20
= 260
Answer(s): 260
