The average height of a group of girls was 135 cm. After 7 boys with a total of 1050 cm joined the group, the average height of all the students increased to 138 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Students |
Number |
1 u |
7 |
1 u + 7 |
Value |
135 |
? |
138 |
Total value |
135 u |
1050 |
138 u + 966 |
(a)
Average height of boys
= 1050 ÷ 7
= 150 cm
(b)
Total height of students
= 138(1 u + 7)
= 138 u + 966
Total height of girls and boys = 135 u + 1050
138 u + 966 = 135 u + 1050
138 u - 135 u = 1050 - 966
3 u = 84
1 u = 84 ÷ 3 = 28
Number of girls = 28
Answer(s): (a) 150 cm; (b) 28