1.

Let A and B be too sets containing four and two elements respectively then the number of subsets of set `AxxB` having atleast 3 elements isA. 275B. 510C. 219D. 256

Answer» Correct Answer - C
We have,
n(A) = 4 and n(B) = 2
`therefore n(A xx B) = n(A) xx n(B) = 4xx2=8`
Required number of subsets = `.^(8)C_(3)+.^(8)C_(4)+.^(8)C_(5)+...+.^(8)C_(8)=(underset(r=0)overset(8)Sigma.^(8)C_(r))-(.^(8)C_(0)+.^(8)C_(1)+.^(8)C_(2))=2^(8)-(1+8+28)=219`


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