In an audition of 30 performers, the average score was 49 points. Given that the average score of the girl performers was 60 points and that of the boy performers was 30 points, find the number of boy performers who participated in the audition.
| |
Girl performers |
Boy performers |
Total |
| Number |
1 u |
30 - 1 u |
30 |
| Value |
60 |
30 |
|
| Total value |
60 u |
900 - 30 u |
1470 |
Number of girl performers = 1 u
Number of boy performers = 30 - 1 u
Total score of the girl performers
= 1 u x 60
= 60 u
Total score of the boy performers
= 30 x (30 - 1 u)
= 900 - 30 u
Total score of the performers
= 60 u + 900 - 30 u
= 60 u - 30 u + 900
= 30 u + 900
Total score of the performers
= 30 x 49
= 1470
30 u + 900 = 1470
30 u = 1470 - 900
30 u = 570
1 u = 570 ÷ 30 = 19
Number of boy performers
= 30 - 1 u
= 30 - 19
= 11
Answer(s): 11
