In one Social Studies class of 81 students, 0.125 of the boys and
23 of the girls passed the exam. A total of 41 students passed the exam. How many boys failed the Social Studies exam?
| |
Boys |
Girls |
Total |
| Passed the test |
1 u |
2 p |
41 |
| Failed the test |
7 u |
1 p |
40 |
| Total |
8 u |
3 p |
81 |
0.125 of the boys =
18 of the boys
Total number of boys = 8 u
Total number of girls = 3 p
1 u + 2 p = 41 --- (1)
7 u + 1 p = 81 - 41
7 u + 1 p = 40 --- (2)
Make u the same.
(1)
x77 u + 14 p = 287 --- (3)
(3) - (2)
14 p - 1 p = 287 - 40
13 p = 247
1 p = 247 ÷ 13 = 19
From (2)
Number of boys who failed
= 40 - 1 p
= 40 - 19
= 21
Answer(s): 21
