The average height of a group of girls was 146 cm. After 5 boys with a total of 775 cm joined the group, the average height of all the students increased to 149 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Students |
Number |
1 u |
5 |
1 u + 5 |
Value |
146 |
? |
149 |
Total value |
146 u |
775 |
149 u + 745 |
(a)
Average height of boys
= 775 ÷ 5
= 155 cm
(b)
Total height of students
= 149(1 u + 5)
= 149 u + 745
Total height of girls and boys = 146 u + 775
149 u + 745 = 146 u + 775
149 u - 146 u = 775 - 745
3 u = 30
1 u = 30 ÷ 3 = 10
Number of girls = 10
Answer(s): (a) 155 cm; (b) 10