In an examination 20% students failed in Mathematics and 15% failed in English. If 10% failed in both and those who passed in both numbered 300, then the total number of students who appeared in the examination was?

Option 2 : 400

Let the number of students appeared in the examination be x,

20% students failed in Mathematics = 20% of x = 0.20x

15% failed in English = 15% of x = 0.15x

10% failed in both = 10% of x = 0.10x

Those who passed in both are 300.

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Number of students failed only in mathematics = 0.20x - 0.10x = 0.10x

Number of students failed only in English = 0.15x - 0.10x = 0.05x

Number of students failed in both mathematics and English = 0.10 x

Total number of students failed = 0.10x + 0.05x + 0.10x = 0.25 x

Number of students passed = total number of students appeared - total number of student failed

= x - 0.25 x

= 0.75 x

According to the given information

0.75 x = 300

x = 300 × (100/75)

x = 300 × (4/3)

x = 400