In one Social Studies class of 90 pupils, 0.1 of the girls and
45 of the boys passed the mock exam. A total of 30 pupils passed the mock exam. How many girls failed the Social Studies mock exam?
| |
Girls |
Boys |
Total |
| Passed the test |
1 u |
4 p |
30 |
| Failed the test |
9 u |
1 p |
60 |
| Total |
10 u |
5 p |
90 |
0.1 of the girls =
110 of the girls
Total number of girls = 10 u
Total number of boys = 5 p
1 u + 4 p = 30 --- (1)
9 u + 1 p = 90 - 30
9 u + 1 p = 60 --- (2)
Make u the same.
(1)
x99 u + 36 p = 270 --- (3)
(3) - (2)
36 p - 1 p = 270 - 60
35 p = 210
1 p = 210 ÷ 35 = 6
From (2)
Number of girls who failed
= 60 - 1 p
= 60 - 6
= 54
Answer(s): 54
