The average height of a group of girls was 126 cm. After 3 boys with a total of 405 cm joined the group, the average height of all the pupils increased to 127 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Pupils |
Number |
1 u |
3 |
1 u + 3 |
Value |
126 |
? |
127 |
Total value |
126 u |
405 |
127 u + 381 |
(a)
Average height of boys
= 405 ÷ 3
= 135 cm
(b)
Total height of pupils
= 127(1 u + 3)
= 127 u + 381
Total height of girls and boys = 126 u + 405
127 u + 381 = 126 u + 405
127 u - 126 u = 405 - 381
1 u = 24
1 u = 24 ÷ 1 = 24
Number of girls = 24
Answer(s): (a) 135 cm; (b) 24