The average height of a group of boys was 125 cm. After 5 girls with a total of 725 cm joined the group, the average height of all the children increased to 135 cm.
- What was the average height of the girls?
- How many boys were there in the group?
|
Boys |
Girls |
Children |
Number |
1 u |
5 |
1 u + 5 |
Value |
125 |
? |
135 |
Total value |
125 u |
725 |
135 u + 675 |
(a)
Average height of girls
= 725 ÷ 5
= 145 cm
(b)
Total height of children
= 135(1 u + 5)
= 135 u + 675
Total height of boys and girls = 125 u + 725
135 u + 675 = 125 u + 725
135 u - 125 u = 725 - 675
10 u = 50
1 u = 50 ÷ 10 = 5
Number of boys = 5
Answer(s): (a) 145 cm; (b) 5