The average height of a group of boys was 151 cm. After 5 girls with a total of 835 cm joined the group, the average height of all the children increased to 156 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 |
151 |
? |
156 |
Total value |
151 u |
835 |
156 u + 780 |
(a)
Average height of girls
= 835 ÷ 5
= 167 cm
(b)
Total height of children
= 156(1 u + 5)
= 156 u + 780
Total height of boys and girls = 151 u + 835
156 u + 780 = 151 u + 835
156 u - 151 u = 835 - 780
5 u = 55
1 u = 55 ÷ 5 = 11
Number of boys = 11
Answer(s): (a) 167 cm; (b) 11