The average height of a group of boys was 119 cm. After 4 girls with a total of 516 cm joined the group, the average height of all the children increased to 123 cm.
- What was the average height of the girls?
- How many boys were there in the group?
|
Boys |
Girls |
Children |
Number |
1 u |
4 |
1 u + 4 |
Value |
119 |
? |
123 |
Total value |
119 u |
516 |
123 u + 492 |
(a)
Average height of girls
= 516 ÷ 4
= 129 cm
(b)
Total height of children
= 123(1 u + 4)
= 123 u + 492
Total height of boys and girls = 119 u + 516
123 u + 492 = 119 u + 516
123 u - 119 u = 516 - 492
4 u = 24
1 u = 24 ÷ 4 = 6
Number of boys = 6
Answer(s): (a) 129 cm; (b) 6