147 students went for a singing competition and 51 of them achieved Silver certificates.
25 of the boys and
14 of the girls achieved Silver certificates. How many boys did not achieve Silver certificates?
| Girls |
Boys |
| 5 u |
4 p |
Achieved
Silver |
Did not achieve
Silver |
Achieved
Silver |
Did not achieve
Silver |
| 2 u |
3 u |
1 p |
3 p |
Number of students who did not achieve Silver certificates
= 147 - 51
= 96
2 u + 1 p = 51
1 p = 51 - 2 u --- (1)
3 u + 3 p = 96
3 p = 96 - 3 u --- (2)
Make p the same.
(1)
x33 p = 153 - 6 u --- (3)
(2) = (3)
96 - 3 u = 153 - 6 u
6 u - 3 u = 153 - 96
3 u = 57
1 u = 57 ÷ 3 = 19
Number of girls who achieved Silver certificates
= 2 u
= 2 x 19
= 38
Number of boys who achieved Silver certificates
= 51 - 38
= 13
Answer(s): 13
