21 pupils in a class sold an average of 18 vintage toy cars for charity. There were 7 more girls than boys in the class. The average number of vintage toy cars sold by the girls was 15. Find the average number of vintage toy cars sold by the boys.
| |
Boys |
Girls |
Total |
| Number |
1 u |
1 u + 7 |
21 |
| Value |
? |
15 |
18 |
| Total value |
168 |
210 |
378 |
Total number of vintage toy cars sold
= 21 x 18
= 378
Number of boys = 1 u
Number of girls = 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 girls in class
= 1 u + 7
= 7 + 7
= 14
Number of vintage toy cars sold by girls
= 14 x 15
= 210
Number of vintage toy cars sold by boys
= 378 - 210
= 168
Average number of vintage toy cars sold by boys
= 168 ÷ 7
= 24
Answer(s): 24
