JEE Main20207 Jan 2020Evening ShiftMathematicsSets and RelationsActual
Let X = n ∈ N : 1 ≤ n ≤ 50 . If A = n ∈ X :   n  i s  a  m u l t i p l e  o f   2 and B = n ∈ X :   n  i s  a  m u l t i p l e  o f  7 , then the number of elements in the smallest subset of X , containing both A and B , is.
Correct answer
29
Step-by-step solution
Here, A = 2 , 4 , 6 , . . . . 50 and B = 7 , 14 , . . . 49 Required smallest subset is A ∪ B . So, n A ∪ B = n A + n B - n A ∩ B = 25 + 7 - 3 = 29 .