The average height of a group of girls was 126 cm. After 6 boys with a total of 834 cm joined the group, the average height of all the pupils increased to 132 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Pupils |
Number |
1 u |
6 |
1 u + 6 |
Value |
126 |
? |
132 |
Total value |
126 u |
834 |
132 u + 792 |
(a)
Average height of boys
= 834 ÷ 6
= 139 cm
(b)
Total height of pupils
= 132(1 u + 6)
= 132 u + 792
Total height of girls and boys = 126 u + 834
132 u + 792 = 126 u + 834
132 u - 126 u = 834 - 792
6 u = 42
1 u = 42 ÷ 6 = 7
Number of girls = 7
Answer(s): (a) 139 cm; (b) 7