The average height of a group of boys was 142 cm. After 9 girls with a total of 1422 cm joined the group, the average height of all the students increased to 150 cm.
- What was the average height of the girls?
- How many boys were there in the group?
|
Boys |
Girls |
Students |
Number |
1 u |
9 |
1 u + 9 |
Value |
142 |
? |
150 |
Total value |
142 u |
1422 |
150 u + 1350 |
(a)
Average height of girls
= 1422 ÷ 9
= 158 cm
(b)
Total height of students
= 150(1 u + 9)
= 150 u + 1350
Total height of boys and girls = 142 u + 1422
150 u + 1350 = 142 u + 1422
150 u - 142 u = 1422 - 1350
8 u = 72
1 u = 72 ÷ 8 = 9
Number of boys = 9
Answer(s): (a) 158 cm; (b) 9