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JEE Main20204 Sep 2020Evening ShiftMathematicsSets and RelationsActual

Let ∪ i = 1 50 X i = ∪ i = 1 n Y i = T , where each X i contains 10 elements and each Y i contains 5 elements. If each element of the set T is an element of exactly 20 of sets X i 's and exactly 6 of sets Y i 's then n is equal to :

Options

  1. A15
  2. B50
  3. C45
  4. D30

Correct answer

D. 30

Step-by-step solution

∪ i = 1 50 X i = ∪ i = 1 n Y i = T From question's conditions 10 × 50 20 = 5 n 6 ⇒ n = 30

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