The average height of a group of boys was 121 cm. After 4 girls with a total of 556 cm joined the group, the average height of all the pupils increased to 127 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 |
121 |
? |
127 |
Total value |
121 u |
556 |
127 u + 508 |
(a)
Average height of girls
= 556 ÷ 4
= 139 cm
(b)
Total height of pupils
= 127(1 u + 4)
= 127 u + 508
Total height of boys and girls = 121 u + 556
127 u + 508 = 121 u + 556
127 u - 121 u = 556 - 508
6 u = 48
1 u = 48 ÷ 6 = 8
Number of boys = 8
Answer(s): (a) 139 cm; (b) 8