The average height of a group of girls was 136 cm. After 8 boys with a total of 1200 cm joined the group, the average height of all the students increased to 140 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Students |
Number |
1 u |
8 |
1 u + 8 |
Value |
136 |
? |
140 |
Total value |
136 u |
1200 |
140 u + 1120 |
(a)
Average height of boys
= 1200 ÷ 8
= 150 cm
(b)
Total height of students
= 140(1 u + 8)
= 140 u + 1120
Total height of girls and boys = 136 u + 1200
140 u + 1120 = 136 u + 1200
140 u - 136 u = 1200 - 1120
4 u = 80
1 u = 80 ÷ 4 = 20
Number of girls = 20
Answer(s): (a) 150 cm; (b) 20