138 pupils went for a dancing competition and 59 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 pupils who did not achieve Silver certificates
= 138 - 59
= 79
3 u + 1 p = 59
1 p = 59 - 3 u --- (1)
2 u + 3 p = 79
3 p = 79 - 2 u --- (2)
Make p the same.
(1)
x33 p = 177 - 9 u --- (3)
(2) = (3)
79 - 2 u = 177 - 9 u
9 u - 2 u = 177 - 79
7 u = 98
1 u = 98 ÷ 7 = 14
Number of boys who did not achieve Silver certificates
= 2 u
= 2 x 14
= 28
Number of girls who did not achieve Silver certificates
= 79 - 28
= 51
Answer(s): 51
