The average height of a group of girls was 168 cm. After 5 boys with a total of 890 cm joined the group, the average height of all the pupils increased to 173 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Pupils |
Number |
1 u |
5 |
1 u + 5 |
Value |
168 |
? |
173 |
Total value |
168 u |
890 |
173 u + 865 |
(a)
Average height of boys
= 890 ÷ 5
= 178 cm
(b)
Total height of pupils
= 173(1 u + 5)
= 173 u + 865
Total height of girls and boys = 168 u + 890
173 u + 865 = 168 u + 890
173 u - 168 u = 890 - 865
5 u = 25
1 u = 25 ÷ 5 = 5
Number of girls = 5
Answer(s): (a) 178 cm; (b) 5