Let R be the set of families having a radio and T the set families having a T.V., then n(R∪T)= The number of families having at least on of the radio and T.V. =1003−63=940 n(R)=794 and n(T)=187 Let x families have both a radio and a T.V. Then number of families who have only radio =794−x And the number of families who have only T.V. =187−x From Venn diagram, 794−x+x−187−x=940 ⇒981−x=940 or x=981−940=41 Hence, the required number of families having both a radio and a T.V. =41