The average height of a group of girls was 123 cm. After 7 boys with a total of 1029 cm joined the group, the average height of all the students increased to 135 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 |
123 |
? |
135 |
Total value |
123 u |
1029 |
135 u + 945 |
(a)
Average height of boys
= 1029 ÷ 7
= 147 cm
(b)
Total height of students
= 135(1 u + 7)
= 135 u + 945
Total height of girls and boys = 123 u + 1029
135 u + 945 = 123 u + 1029
135 u - 123 u = 1029 - 945
12 u = 84
1 u = 84 ÷ 12 = 7
Number of girls = 7
Answer(s): (a) 147 cm; (b) 7