The average height of a group of girls was 140 cm. After 6 boys with a total of 882 cm joined the group, the average height of all the children increased to 142 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 |
140 |
? |
142 |
Total value |
140 u |
882 |
142 u + 852 |
(a)
Average height of boys
= 882 ÷ 6
= 147 cm
(b)
Total height of children
= 142(1 u + 6)
= 142 u + 852
Total height of girls and boys = 140 u + 882
142 u + 852 = 140 u + 882
142 u - 140 u = 882 - 852
2 u = 30
1 u = 30 ÷ 2 = 15
Number of girls = 15
Answer(s): (a) 147 cm; (b) 15