The average height of a group of girls was 159 cm. After 6 boys with a total of 1056 cm joined the group, the average height of all the children increased to 165 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Children |
Number |
1 u |
6 |
1 u + 6 |
Value |
159 |
? |
165 |
Total value |
159 u |
1056 |
165 u + 990 |
(a)
Average height of boys
= 1056 ÷ 6
= 176 cm
(b)
Total height of children
= 165(1 u + 6)
= 165 u + 990
Total height of girls and boys = 159 u + 1056
165 u + 990 = 159 u + 1056
165 u - 159 u = 1056 - 990
6 u = 66
1 u = 66 ÷ 6 = 11
Number of girls = 11
Answer(s): (a) 176 cm; (b) 11