In one Mathematics class of 80 pupils, 0.25 of the boys and
45 of the girls passed the mock test. A total of 42 pupils passed the mock test. How many boys failed the Mathematics mock test?
| |
Boys |
Girls |
Total |
| Passed the test |
1 u |
4 p |
42 |
| Failed the test |
3 u |
1 p |
38 |
| Total |
4 u |
5 p |
80 |
0.25 of the boys =
14 of the boys
Total number of boys = 4 u
Total number of girls = 5 p
1 u + 4 p = 42 --- (1)
3 u + 1 p = 80 - 42
3 u + 1 p = 38 --- (2)
Make u the same.
(1)
x33 u + 12 p = 126 --- (3)
(3) - (2)
12 p - 1 p = 126 - 38
11 p = 88
1 p = 88 ÷ 11 = 8
From (2)
Number of boys who failed
= 38 - 1 p
= 38 - 8
= 30
Answer(s): 30
