The average height of a group of boys was 164 cm. After 7 girls with a total of 1232 cm joined the group, the average height of all the pupils increased to 166 cm.
- What was the average height of the girls?
- How many boys were there in the group?
|
Boys |
Girls |
Pupils |
Number |
1 u |
7 |
1 u + 7 |
Value |
164 |
? |
166 |
Total value |
164 u |
1232 |
166 u + 1162 |
(a)
Average height of girls
= 1232 ÷ 7
= 176 cm
(b)
Total height of pupils
= 166(1 u + 7)
= 166 u + 1162
Total height of boys and girls = 164 u + 1232
166 u + 1162 = 164 u + 1232
166 u - 164 u = 1232 - 1162
2 u = 70
1 u = 70 ÷ 2 = 35
Number of boys = 35
Answer(s): (a) 176 cm; (b) 35