The average height of a group of girls was 151 cm. After 6 boys with a total of 954 cm joined the group, the average height of all the pupils increased to 153 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Pupils |
Number |
1 u |
6 |
1 u + 6 |
Value |
151 |
? |
153 |
Total value |
151 u |
954 |
153 u + 918 |
(a)
Average height of boys
= 954 ÷ 6
= 159 cm
(b)
Total height of pupils
= 153(1 u + 6)
= 153 u + 918
Total height of girls and boys = 151 u + 954
153 u + 918 = 151 u + 954
153 u - 151 u = 954 - 918
2 u = 36
1 u = 36 ÷ 2 = 18
Number of girls = 18
Answer(s): (a) 159 cm; (b) 18