JEE Main202228 Jun 2022Morning ShiftMathematicsSets and RelationsActual
Let R 1 and R 2 be relations on the set 1 , 2 , … , 50 such that R 1 = p , p n : p is a prime and n ≥ 0 is an integer and R 2 = p , p n : p is a prime and n = 0 or 1 . Then, the number of elements in R 1 - R 2 is ____.
Correct answer
0
Step-by-step solution
Here, p , p n ∈ 1 , 2 , … 50 Now p can take values 2 , 3 , 5 , 7 , 11 , 13 , 17 , 23 , 29 , 31 , 37 , 41 , 43 and 47 . ∴ R 1 = 2 , 2 0 , 2 , 2 1 … 2 , 2 5 , 3 , 3 0 , … 3 , 3 3 , 5 , 5 0 , … 5 , 5 2 , 7 , 7 0 , … 7 , 7 2 , 11 , 11 0 , 11 , 11 1 , . . . 47 , 47 0 , 47 , 47 1 R 2 = 2 , 2 0 , 2 , 2 1 , 3 , 3 0 , 3 , 3 1 . . . . 47 , 47 0 , 47 , 47 1 Now R 1 - R 2 ≡ R 1 ∩ R 2 ' So R 1 - R 2 = 2 , 2 2 , 2 , 2 3 , 2 , 2 4 , 2 , 2 5 , 3 , 3 2 , 3 , 3 3 , 5 , 5 2 , 7 ,