The interview!!
Algebra
Level
5
Three ladies each brought a child for admission to a school . The head of the school wishes to interview six people one by one , taking case that no child is interviewed before its mother . The no. Of different ways, this can be done is?
90
72
20
720
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1 solution
Let the mothers be A , B and D and their respective children a,b,d . CASE-1 : when each mother is followed by her child i.e. Aa, Bb,Dd . This can be done in 6 ways. CASE-2: AB ab Dd interview in this order may be conducted in 12 ways . Similarly order type Dd AB ab again in 12 ways . CASE -3: AB aD bd this order of interview can be conducted in 24 ways . CASE-4 : ABD abd this order of interview, can be conducted in 36 ways . Total number of ways= 90