20 pupils in a class sold an average of 16 cards for charity. There were 4 more boys than girls in the class. The average number of cards sold by the boys was 12. Find the average number of cards sold by the girls.
| |
Girls |
Boys |
Total |
| Number |
1 u |
1 u + 4 |
20 |
| Value |
? |
12 |
16 |
| Total value |
176 |
144 |
320 |
Total number of cards sold
= 20 x 16
= 320
Number of girls = 1 u
Number of boys = 1 u + 4
1 u + 1 u + 4 = 20
2 u + 4 = 20
2 u = 20 - 4
2 u = 16
1 u = 16 ÷ 2 = 8
Number of boys in class
= 1 u + 4
= 8 + 4
= 12
Number of cards sold by boys
= 12 x 12
= 144
Number of cards sold by girls
= 320 - 144
= 176
Average number of cards sold by girls
= 176 ÷ 8
= 22
Answer(s): 22
