155 pupils went for a dancing competition and 43 of them achieved Silver certificates.
25 of the girls and
15 of the boys achieved Silver certificates. How many girls did not achieve Silver certificates?
| Boys |
Girls |
| 5 u |
5 p |
Achieved
Silver |
Did not achieve
Silver |
Achieved
Silver |
Did not achieve
Silver |
| 2 u |
3 u |
1 p |
4 p |
Number of pupils who did not achieve Silver certificates
= 155 - 43
= 112
2 u + 1 p = 43
1 p = 43 - 2 u --- (1)
3 u + 4 p = 112
4 p = 112 - 3 u --- (2)
Make p the same.
(1)
x44 p = 172 - 8 u --- (3)
(2) = (3)
112 - 3 u = 172 - 8 u
8 u - 3 u = 172 - 112
5 u = 60
1 u = 60 ÷ 5 = 12
Number of boys who achieved Silver certificates
= 2 u
= 2 x 12
= 24
Number of girls who achieved Silver certificates
= 43 - 24
= 19
Answer(s): 19
