33 pupils in a class sold an average of 20 buttons for charity. There were 9 more girls than boys in the class. The average number of buttons sold by the girls was 16. Find the average number of buttons sold by the boys.
|
Boys |
Girls |
Total |
Number |
1 u |
1 u + 9 |
33 |
Value |
? |
16 |
20 |
Total value |
324 |
336 |
660 |
Total number of buttons sold
= 33 x 20
= 660
Number of boys = 1 u
Number of girls = 1 u + 9
1 u + 1 u + 9 = 33
2 u + 9 = 33
2 u = 33 - 9
2 u = 24
1 u = 24 ÷ 2 = 12
Number of girls in class
= 1 u + 9
= 12 + 9
= 21
Number of buttons sold by girls
= 21 x 16
= 336
Number of buttons sold by boys
= 660 - 336
= 324
Average number of buttons sold by boys
= 324 ÷ 12
= 27
Answer(s): 27