The average height of a group of boys was 139 cm. After 5 girls with a total of 755 cm joined the group, the average height of all the children increased to 140 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 |
139 |
? |
140 |
Total value |
139 u |
755 |
140 u + 700 |
(a)
Average height of girls
= 755 ÷ 5
= 151 cm
(b)
Total height of children
= 140(1 u + 5)
= 140 u + 700
Total height of boys and girls = 139 u + 755
140 u + 700 = 139 u + 755
140 u - 139 u = 755 - 700
1 u = 55
1 u = 55 ÷ 1 = 55
Number of boys = 55
Answer(s): (a) 151 cm; (b) 55