In an audition of 30 contestants, the average score was 58 points. Given that the average score of the girl contestants was 70 points and that of the boy contestants was 30 points, find the number of boy contestants who participated in the audition.
| |
Girl contestants |
Boy contestants |
Total |
| Number |
1 u |
30 - 1 u |
30 |
| Value |
70 |
30 |
|
| Total value |
70 u |
900 - 30 u |
1740 |
Number of girl contestants = 1 u
Number of boy contestants = 30 - 1 u
Total score of the girl contestants
= 1 u x 70
= 70 u
Total score of the boy contestants
= 30 x (30 - 1 u)
= 900 - 30 u
Total score of the contestants
= 70 u + 900 - 30 u
= 70 u - 30 u + 900
= 40 u + 900
Total score of the contestants
= 30 x 58
= 1740
40 u + 900 = 1740
40 u = 1740 - 900
40 u = 840
1 u = 840 ÷ 40 = 21
Number of boy contestants
= 30 - 1 u
= 30 - 21
= 9
Answer(s): 9
