The average height of a group of girls was 145 cm. After 5 boys with a total of 785 cm joined the group, the average height of all the children increased to 147 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Children |
Number |
1 u |
5 |
1 u + 5 |
Value |
145 |
? |
147 |
Total value |
145 u |
785 |
147 u + 735 |
(a)
Average height of boys
= 785 ÷ 5
= 157 cm
(b)
Total height of children
= 147(1 u + 5)
= 147 u + 735
Total height of girls and boys = 145 u + 785
147 u + 735 = 145 u + 785
147 u - 145 u = 785 - 735
2 u = 50
1 u = 50 ÷ 2 = 25
Number of girls = 25
Answer(s): (a) 157 cm; (b) 25