131 pupils went for a singing competition and 41 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 pupils who did not achieve Silver certificates
= 131 - 41
= 90
2 u + 1 p = 41
1 p = 41 - 2 u --- (1)
3 u + 3 p = 90
3 p = 90 - 3 u --- (2)
Make p the same.
(1)
x33 p = 123 - 6 u --- (3)
(2) = (3)
90 - 3 u = 123 - 6 u
6 u - 3 u = 123 - 90
3 u = 33
1 u = 33 ÷ 3 = 11
Number of girls who achieved Silver certificates
= 2 u
= 2 x 11
= 22
Number of boys who achieved Silver certificates
= 41 - 22
= 19
Answer(s): 19