The average height of a group of girls was 122 cm. After 9 boys with a total of 1278 cm joined the group, the average height of all the children increased to 134 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Children |
Number |
1 u |
9 |
1 u + 9 |
Value |
122 |
? |
134 |
Total value |
122 u |
1278 |
134 u + 1206 |
(a)
Average height of boys
= 1278 ÷ 9
= 142 cm
(b)
Total height of children
= 134(1 u + 9)
= 134 u + 1206
Total height of girls and boys = 122 u + 1278
134 u + 1206 = 122 u + 1278
134 u - 122 u = 1278 - 1206
12 u = 72
1 u = 72 ÷ 12 = 6
Number of girls = 6
Answer(s): (a) 142 cm; (b) 6