Q5. If X and Y are two sets such that X has 40 elements, X $\cup$ Y has 60 elements and X $\cap$  Y has 10 elements, how many elements does Y have?

S seema garhwal

n( X $\cup$ Y) = 60

n( X ∩ Y) = 10

n(X) = 40

n( X $\cup$ Y) =  n(X)  +  n(Y)   -  n( X ∩ Y)

n(Y) = 60 - 40 + 10

n(Y) = 30

Hence,set Y has 30 elements.

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