The average height of a group of girls was 140 cm. After 4 boys with a total of 596 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 |
4 |
1 u + 4 |
Value |
140 |
? |
141 |
Total value |
140 u |
596 |
141 u + 564 |
(a)
Average height of boys
= 596 ÷ 4
= 149 cm
(b)
Total height of children
= 141(1 u + 4)
= 141 u + 564
Total height of girls and boys = 140 u + 596
141 u + 564 = 140 u + 596
141 u - 140 u = 596 - 564
1 u = 32
1 u = 32 ÷ 1 = 32
Number of girls = 32
Answer(s): (a) 149 cm; (b) 32