The average height of a group of boys was 107 cm. After 3 girls with a total of 375 cm joined the group, the average height of all the pupils increased to 113 cm.
- What was the average height of the girls?
- How many boys were there in the group?
|
Boys |
Girls |
Pupils |
Number |
1 u |
3 |
1 u + 3 |
Value |
107 |
? |
113 |
Total value |
107 u |
375 |
113 u + 339 |
(a)
Average height of girls
= 375 ÷ 3
= 125 cm
(b)
Total height of pupils
= 113(1 u + 3)
= 113 u + 339
Total height of boys and girls = 107 u + 375
113 u + 339 = 107 u + 375
113 u - 107 u = 375 - 339
6 u = 36
1 u = 36 ÷ 6 = 6
Number of boys = 6
Answer(s): (a) 125 cm; (b) 6