The average height of a group of boys was 131 cm. After 9 girls with a total of 1278 cm joined the group, the average height of all the students increased to 132 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 |
131 |
? |
132 |
Total value |
131 u |
1278 |
132 u + 1188 |
(a)
Average height of girls
= 1278 ÷ 9
= 142 cm
(b)
Total height of students
= 132(1 u + 9)
= 132 u + 1188
Total height of boys and girls = 131 u + 1278
132 u + 1188 = 131 u + 1278
132 u - 131 u = 1278 - 1188
1 u = 90
1 u = 90 ÷ 1 = 90
Number of boys = 90
Answer(s): (a) 142 cm; (b) 90