The average height of a group of boys was 130 cm. After 3 girls with a total of 438 cm joined the group, the average height of all the students increased to 136 cm.
- What was the average height of the girls?
- How many boys were there in the group?
|
Boys |
Girls |
Students |
Number |
1 u |
3 |
1 u + 3 |
Value |
130 |
? |
136 |
Total value |
130 u |
438 |
136 u + 408 |
(a)
Average height of girls
= 438 ÷ 3
= 146 cm
(b)
Total height of students
= 136(1 u + 3)
= 136 u + 408
Total height of boys and girls = 130 u + 438
136 u + 408 = 130 u + 438
136 u - 130 u = 438 - 408
6 u = 30
1 u = 30 ÷ 6 = 5
Number of boys = 5
Answer(s): (a) 146 cm; (b) 5