27 children in a class sold an average of 17 postcards for charity. There were 9 more boys than girls in the class. The average number of postcards sold by the boys was 13. Find the average number of postcards sold by the girls.
|
Girls |
Boys |
Total |
Number |
1 u |
1 u + 9 |
27 |
Value |
? |
13 |
17 |
Total value |
225 |
234 |
459 |
Total number of postcards sold
= 27 x 17
= 459
Number of girls = 1 u
Number of boys = 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 boys in class
= 1 u + 9
= 9 + 9
= 18
Number of postcards sold by boys
= 18 x 13
= 234
Number of postcards sold by girls
= 459 - 234
= 225
Average number of postcards sold by girls
= 225 ÷ 9
= 25
Answer(s): 25