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Solution


Q.

If A is the void set ϕ, then P(A) has just one element ϕ, i.e., P(ϕ)={ϕ}. So number of elements of P[P(P(ϕ))] is _________.

Ans.

(4)

We have, P(ϕ)={ϕ}

∴  P(P(ϕ))={ϕ,{ϕ}}⇒P[P(P(ϕ))]={ϕ, {ϕ}, {{ϕ}}, {ϕ, {ϕ}}}