20 students in a class sold an average of 21 comic books for charity. There were 8 more girls than boys in the class. The average number of comic books sold by the girls was 15. Find the average number of comic books sold by the boys.
| |
Boys |
Girls |
Total |
| Number |
1 u |
1 u + 8 |
20 |
| Value |
? |
15 |
21 |
| Total value |
210 |
210 |
420 |
Total number of comic books sold
= 20 x 21
= 420
Number of boys = 1 u
Number of girls = 1 u + 8
1 u + 1 u + 8 = 20
2 u + 8 = 20
2 u = 20 - 8
2 u = 12
1 u = 12 ÷ 2 = 6
Number of girls in class
= 1 u + 8
= 6 + 8
= 14
Number of comic books sold by girls
= 14 x 15
= 210
Number of comic books sold by boys
= 420 - 210
= 210
Average number of comic books sold by boys
= 210 ÷ 6
= 35
Answer(s): 35
