The average height of a group of girls was 113 cm. After 9 boys with a total of 1143 cm joined the group, the average height of all the children increased to 122 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 |
113 |
? |
122 |
Total value |
113 u |
1143 |
122 u + 1098 |
(a)
Average height of boys
= 1143 ÷ 9
= 127 cm
(b)
Total height of children
= 122(1 u + 9)
= 122 u + 1098
Total height of girls and boys = 113 u + 1143
122 u + 1098 = 113 u + 1143
122 u - 113 u = 1143 - 1098
9 u = 45
1 u = 45 ÷ 9 = 5
Number of girls = 5
Answer(s): (a) 127 cm; (b) 5