The average height of a group of boys was 120 cm. After 4 girls with a total of 536 cm joined the group, the average height of all the pupils increased to 124 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 |
120 |
? |
124 |
Total value |
120 u |
536 |
124 u + 496 |
(a)
Average height of girls
= 536 ÷ 4
= 134 cm
(b)
Total height of pupils
= 124(1 u + 4)
= 124 u + 496
Total height of boys and girls = 120 u + 536
124 u + 496 = 120 u + 536
124 u - 120 u = 536 - 496
4 u = 40
1 u = 40 ÷ 4 = 10
Number of boys = 10
Answer(s): (a) 134 cm; (b) 10