The average height of a group of girls was 137 cm. After 6 boys with a total of 906 cm joined the group, the average height of all the children increased to 141 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 |
137 |
? |
141 |
Total value |
137 u |
906 |
141 u + 846 |
(a)
Average height of boys
= 906 ÷ 6
= 151 cm
(b)
Total height of children
= 141(1 u + 6)
= 141 u + 846
Total height of girls and boys = 137 u + 906
141 u + 846 = 137 u + 906
141 u - 137 u = 906 - 846
4 u = 60
1 u = 60 ÷ 4 = 15
Number of girls = 15
Answer(s): (a) 151 cm; (b) 15