The average height of a group of girls was 165 cm. After 7 boys with a total of 1281 cm joined the group, the average height of all the children increased to 172 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Children |
Number |
1 u |
7 |
1 u + 7 |
Value |
165 |
? |
172 |
Total value |
165 u |
1281 |
172 u + 1204 |
(a)
Average height of boys
= 1281 ÷ 7
= 183 cm
(b)
Total height of children
= 172(1 u + 7)
= 172 u + 1204
Total height of girls and boys = 165 u + 1281
172 u + 1204 = 165 u + 1281
172 u - 165 u = 1281 - 1204
7 u = 77
1 u = 77 ÷ 7 = 11
Number of girls = 11
Answer(s): (a) 183 cm; (b) 11