113 students went for a singing competition and 51 of them achieved Silver certificates.
35 of the girls and
14 of the boys achieved Silver certificates. How many girls did not achieve Silver certificates?
| Boys |
Girls |
| 5 u |
4 p |
Achieved
Silver |
Did not achieve
Silver |
Achieved
Silver |
Did not achieve
Silver |
| 3 u |
2 u |
1 p |
3 p |
Number of students who did not achieve Silver certificates
= 113 - 51
= 62
3 u + 1 p = 51
1 p = 51 - 3 u --- (1)
2 u + 3 p = 62
3 p = 62 - 2 u --- (2)
Make p the same.
(1)
x33 p = 153 - 9 u --- (3)
(2) = (3)
62 - 2 u = 153 - 9 u
9 u - 2 u = 153 - 62
7 u = 91
1 u = 91 ÷ 7 = 13
Number of boys who achieved Silver certificates
= 3 u
= 3 x 13
= 39
Number of girls who achieved Silver certificates
= 51 - 39
= 12
Answer(s): 12
