Question

JEE MAINS MATHS QUESTION SEPTEMBER 2020

Answer 1

In a group 63% people read news paper A while 76% people read news paper B.

To find : x% people read both A and B. then value of x may be..

solution : let n(u) is total no of people

n(A) is no of people reading news paper A

n(B) is no of people reading news paper B.

if 63 % people read news A and 76% people read news B then definitely less than or equal to 100 % people read news A or news B.

i.e., n(A ∪ B) ≤ 100

⇒n(A) + n(B) - n(A ∩ B) ≤ 100

⇒63 + 76 - x ≤ 100

⇒139 - x ≤ 100

⇒x ≤ 39 .....(1)

but we know, n(A ∩ B) ≤ n(A)

so, x ≤ 63 .....(2)

from equations (1) and (2) we get,

39 ≤ x ≤ 63

now see only option (4) 55, is correct choice.

Therefore the value of x may be 55 %