The average height of a group of girls was 142 cm. After 8 boys with a total of 1224 cm joined the group, the average height of all the children increased to 144 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Children |
Number |
1 u |
8 |
1 u + 8 |
Value |
142 |
? |
144 |
Total value |
142 u |
1224 |
144 u + 1152 |
(a)
Average height of boys
= 1224 ÷ 8
= 153 cm
(b)
Total height of children
= 144(1 u + 8)
= 144 u + 1152
Total height of girls and boys = 142 u + 1224
144 u + 1152 = 142 u + 1224
144 u - 142 u = 1224 - 1152
2 u = 72
1 u = 72 ÷ 2 = 36
Number of girls = 36
Answer(s): (a) 153 cm; (b) 36