Answer :

Given that 52 families out of 82 families have at most 2 children.


It is told that 20 families need to be selected with at least 18 families having utmost 2 children.


The following are the cases:


i. 18 families having at most 2 children and 2 from other families


ii. 19 families are having at most 2 children and 1 from other families


iii. 20 families having at most 2 children


Let us assume that the no. of ways choosing to be N.


N = (Selecting 18 families having at most 2 children and 2 from other families) + (Selecting 19 families having at most 2 children and 1 from other families) + (Selecting 20 families having at most 2 children)


N = (52C18 × 35C2) + (52C19 × 35C1) + (52C20)


We know that ,


And also n! = (n)(n – 1)......2.1







The no. of ways of choosing 18 families are .


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