21 children in a class sold an average of 21 comic books for charity. There were 7 more boys than girls in the class. The average number of comic books sold by the boys was 17. Find the average number of comic books sold by the girls.
| |
Girls |
Boys |
Total |
| Number |
1 u |
1 u + 7 |
21 |
| Value |
? |
17 |
21 |
| Total value |
203 |
238 |
441 |
Total number of comic books sold
= 21 x 21
= 441
Number of girls = 1 u
Number of boys = 1 u + 7
1 u + 1 u + 7 = 21
2 u + 7 = 21
2 u = 21 - 7
2 u = 14
1 u = 14 ÷ 2 = 7
Number of boys in class
= 1 u + 7
= 7 + 7
= 14
Number of comic books sold by boys
= 14 x 17
= 238
Number of comic books sold by girls
= 441 - 238
= 203
Average number of comic books sold by girls
= 203 ÷ 7
= 29
Answer(s): 29
