The average height of a group of girls was 150 cm. After 4 boys with a total of 644 cm joined the group, the average height of all the children increased to 154 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 |
150 |
? |
154 |
Total value |
150 u |
644 |
154 u + 616 |
(a)
Average height of boys
= 644 ÷ 4
= 161 cm
(b)
Total height of children
= 154(1 u + 4)
= 154 u + 616
Total height of girls and boys = 150 u + 644
154 u + 616 = 150 u + 644
154 u - 150 u = 644 - 616
4 u = 28
1 u = 28 ÷ 4 = 7
Number of girls = 7
Answer(s): (a) 161 cm; (b) 7