The average height of a group of girls was 143 cm. After 3 boys with a total of 471 cm joined the group, the average height of all the children increased to 145 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Children |
Number |
1 u |
3 |
1 u + 3 |
Value |
143 |
? |
145 |
Total value |
143 u |
471 |
145 u + 435 |
(a)
Average height of boys
= 471 ÷ 3
= 157 cm
(b)
Total height of children
= 145(1 u + 3)
= 145 u + 435
Total height of girls and boys = 143 u + 471
145 u + 435 = 143 u + 471
145 u - 143 u = 471 - 435
2 u = 36
1 u = 36 ÷ 2 = 18
Number of girls = 18
Answer(s): (a) 157 cm; (b) 18