Let B1 be the event where Box-I is selected. &B2→ where box-II selected P(B1)=P(B2)=
1
2
Let E be the event where selected card is nonprime. For B1 : Prime numbers : {2, 3, 5, 7, 11, 13, 17, 19, 23, 29} For B2 : Prime numbers : {31, 37, 41, 43, 47} P(E)=P(B1)×P(