27 pupils in a class sold an average of 16 pens for charity. There were 9 more girls than boys in the class. The average number of pens sold by the girls was 12. Find the average number of pens sold by the boys.
|
Boys |
Girls |
Total |
Number |
1 u |
1 u + 9 |
27 |
Value |
? |
12 |
16 |
Total value |
216 |
216 |
432 |
Total number of pens sold
= 27 x 16
= 432
Number of boys = 1 u
Number of girls = 1 u + 9
1 u + 1 u + 9 = 27
2 u + 9 = 27
2 u = 27 - 9
2 u = 18
1 u = 18 ÷ 2 = 9
Number of girls in class
= 1 u + 9
= 9 + 9
= 18
Number of pens sold by girls
= 18 x 12
= 216
Number of pens sold by boys
= 432 - 216
= 216
Average number of pens sold by boys
= 216 ÷ 9
= 24
Answer(s): 24