1.

Let A and B two sets containing four and two elements respectively, The number of subsets of the set A × B, each having at least three elements is:1. 2702. 2393. 2194. 256

Answer» Correct Answer - Option 3 : 219

Concept:

Selection r things out of n things is denoted by nCr 

nCr = \(\rm \frac {n!}{(n-r)!r!}\)

 

Calculation:

Set A has 4 elements

Set B has 2 elements

Total number of element in (A × B) = 4 × 2 = 8

Total number of subsets of (A × B) = 28 = 256

Number of subsets having 0 element = 8​C0 ​= 1

Number of subsets having 1 element = 8​C1​ = 8

Number of subsets having 2 elements = 8​C2 ​= (8 × 7)/2 ​= 28

Number of subsets having at least 3 elements

= 256 – 28 – 8 – 1 = 219

Hence, option (3) is correct.



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