170 pupils went for a physical fitness test and 72 of them achieved Silver certificates.
35 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 |
| 3 u |
2 u |
1 p |
4 p |
Number of pupils who did not achieve Silver certificates
= 170 - 72
= 98
3 u + 1 p = 72
1 p = 72 - 3 u --- (1)
2 u + 4 p = 98
4 p = 98 - 2 u --- (2)
Make p the same.
(1)
x44 p = 288 - 12 u --- (3)
(2) = (3)
98 - 2 u = 288 - 12 u
12 u - 2 u = 288 - 98
10 u = 190
1 u = 190 ÷ 10 = 19
Number of boys who achieved Silver certificates
= 3 u
= 3 x 19
= 57
Number of girls who achieved Silver certificates
= 72 - 57
= 15
Answer(s): 15
