129 students went for a physical fitness test and 45 of them achieved Silver certificates.
25 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 |
| 2 u |
3 u |
1 p |
3 p |
Number of students who did not achieve Silver certificates
= 129 - 45
= 84
2 u + 1 p = 45
1 p = 45 - 2 u --- (1)
3 u + 3 p = 84
3 p = 84 - 3 u --- (2)
Make p the same.
(1)
x33 p = 135 - 6 u --- (3)
(2) = (3)
84 - 3 u = 135 - 6 u
6 u - 3 u = 135 - 84
3 u = 51
1 u = 51 ÷ 3 = 17
Number of boys who did not achieve Silver certificates
= 3 u
= 3 x 17
= 51
Number of girls who did not achieve Silver certificates
= 84 - 51
= 33
Answer(s): 33
