The average height of a group of boys was 112 cm. After 7 girls with a total of 910 cm joined the group, the average height of all the children increased to 121 cm.
- What was the average height of the girls?
- How many boys were there in the group?
|
Boys |
Girls |
Children |
Number |
1 u |
7 |
1 u + 7 |
Value |
112 |
? |
121 |
Total value |
112 u |
910 |
121 u + 847 |
(a)
Average height of girls
= 910 ÷ 7
= 130 cm
(b)
Total height of children
= 121(1 u + 7)
= 121 u + 847
Total height of boys and girls = 112 u + 910
121 u + 847 = 112 u + 910
121 u - 112 u = 910 - 847
9 u = 63
1 u = 63 ÷ 9 = 7
Number of boys = 7
Answer(s): (a) 130 cm; (b) 7