The average height of a group of boys was 144 cm. After 6 girls with a total of 894 cm joined the group, the average height of all the pupils increased to 145 cm.
- What was the average height of the girls?
- How many boys were there in the group?
|
Boys |
Girls |
Pupils |
Number |
1 u |
6 |
1 u + 6 |
Value |
144 |
? |
145 |
Total value |
144 u |
894 |
145 u + 870 |
(a)
Average height of girls
= 894 ÷ 6
= 149 cm
(b)
Total height of pupils
= 145(1 u + 6)
= 145 u + 870
Total height of boys and girls = 144 u + 894
145 u + 870 = 144 u + 894
145 u - 144 u = 894 - 870
1 u = 24
1 u = 24 ÷ 1 = 24
Number of boys = 24
Answer(s): (a) 149 cm; (b) 24