45 children in a class sold an average of 20 seashells for charity. There were 9 more boys than girls in the class. The average number of seashells sold by the boys was 12. Find the average number of seashells sold by the girls.
| |
Girls |
Boys |
Total |
| Number |
1 u |
1 u + 9 |
45 |
| Value |
? |
12 |
20 |
| Total value |
576 |
324 |
900 |
Total number of seashells sold
= 45 x 20
= 900
Number of girls = 1 u
Number of boys = 1 u + 9
1 u + 1 u + 9 = 45
2 u + 9 = 45
2 u = 45 - 9
2 u = 36
1 u = 36 ÷ 2 = 18
Number of boys in class
= 1 u + 9
= 18 + 9
= 27
Number of seashells sold by boys
= 27 x 12
= 324
Number of seashells sold by girls
= 900 - 324
= 576
Average number of seashells sold by girls
= 576 ÷ 18
= 32
Answer(s): 32
