The average height of a group of girls was 135 cm. After 5 boys with a total of 785 cm joined the group, the average height of all the students increased to 146 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 |
135 |
? |
146 |
Total value |
135 u |
785 |
146 u + 730 |
(a)
Average height of boys
= 785 ÷ 5
= 157 cm
(b)
Total height of students
= 146(1 u + 5)
= 146 u + 730
Total height of girls and boys = 135 u + 785
146 u + 730 = 135 u + 785
146 u - 135 u = 785 - 730
11 u = 55
1 u = 55 ÷ 11 = 5
Number of girls = 5
Answer(s): (a) 157 cm; (b) 5