Tuesday, 9 February 2016

permutations - How many distinct six letter words can be formed from $11$ distinct consonants and $5$ vowels if the middle two letters are vowels?

With eleven distinct consonants and five different vowels, how many distinct six letter words can be formed if middle two letters are occupied by vowels (may be repeated) and first two and last two positions are occupied by consonants (all distinct) ?



I tried Solving it:




$$11 \times 10 \times 5 \times 5 \times 9 \times 8 = 198,000$$



Is this the right approach? I am confused because question says vowels may be repeated.. so do we have to consider two different cases 1) with repetition and 2) without repetition?

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