Question

In a class, 70 students wrote two tests viz; test - I and test - II.
50% of the students failed in test - I and 40% of the students in test - II. How many students passed in both tests?
(a) 21 (b) 7 (c) 28 (d) 14

Answer 1

answer is 77

50% of 70 is 35

40% of 70 is 28

so, 70-35=35

70-28=42

number of students passed in test 1 is 35

number of students passed in test 2 is 42

so, total number of students passed is 77

Answer 2

Answer:

It's 7.

Step-by-step explanation:

The person before me has explained some already, here's one missing step:

If n(A) be whoever passed test 1, and n(B) be whoever passed test 2;

n(A) is 35, n(B) is 42.

n(A) + n(B) - ( whoever passed both tests) = n(total students) = 70

Solving this, 7 people passed both.

P. S. I don't know how to get the proper symbols on my keyboard, suggestions are welcome:)