The average height of a group of girls was 127 cm. After 4 boys with a total of 548 cm joined the group, the average height of all the pupils increased to 131 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Pupils |
Number |
1 u |
4 |
1 u + 4 |
Value |
127 |
? |
131 |
Total value |
127 u |
548 |
131 u + 524 |
(a)
Average height of boys
= 548 ÷ 4
= 137 cm
(b)
Total height of pupils
= 131(1 u + 4)
= 131 u + 524
Total height of girls and boys = 127 u + 548
131 u + 524 = 127 u + 548
131 u - 127 u = 548 - 524
4 u = 24
1 u = 24 ÷ 4 = 6
Number of girls = 6
Answer(s): (a) 137 cm; (b) 6