The average height of a group of boys was 127 cm. After 4 girls with a total of 560 cm joined the group, the average height of all the pupils increased to 131 cm.
- What was the average height of the girls?
- How many boys were there in the group?
|
Boys |
Girls |
Pupils |
Number |
1 u |
4 |
1 u + 4 |
Value |
127 |
? |
131 |
Total value |
127 u |
560 |
131 u + 524 |
(a)
Average height of girls
= 560 ÷ 4
= 140 cm
(b)
Total height of pupils
= 131(1 u + 4)
= 131 u + 524
Total height of boys and girls = 127 u + 560
131 u + 524 = 127 u + 560
131 u - 127 u = 560 - 524
4 u = 36
1 u = 36 ÷ 4 = 9
Number of boys = 9
Answer(s): (a) 140 cm; (b) 9