The average height of a group of girls was 135 cm. After 4 boys with a total of 572 cm joined the group, the average height of all the students increased to 137 cm.
- What was the average height of the boys?
- How many girls were there in the group?
|
Girls |
Boys |
Students |
Number |
1 u |
4 |
1 u + 4 |
Value |
135 |
? |
137 |
Total value |
135 u |
572 |
137 u + 548 |
(a)
Average height of boys
= 572 ÷ 4
= 143 cm
(b)
Total height of students
= 137(1 u + 4)
= 137 u + 548
Total height of girls and boys = 135 u + 572
137 u + 548 = 135 u + 572
137 u - 135 u = 572 - 548
2 u = 24
1 u = 24 ÷ 2 = 12
Number of girls = 12
Answer(s): (a) 143 cm; (b) 12