Question { Google, 34300 }

In a class 80% have passed english,70% passed Hindi 10%
didnot passed either. If 144 students passed both. What is
the total strength of the class.

Answer

let t = total no of students.. then
students who passed one or both subjects,

n(e U h) = n(e) + n(h) - n(e intersection h)
=> t = 0.8t + 0.7t - 144
=> t = 1.5t - 144

students who failed both subjects is 10% i.e. 0.1t
=>t-n(e U h) = 0.1t,
=>t -(1.5t - 144) = 0.1t
=>t- 1.5t- 0.1t = -144
=> -0.6t = -144
=>t = 240