Permutations

Question

i) How many permutations are there of the letters in the word ’REPETITION’?

 

(ii) How many ways can you pair up 8 boys and 8 girls?

Answer 1

(i) of the ten letters, three letters occur twice, so the # distinguishable permutations is not 10!, but 10! divided by [2!2!2!].

 

(ii) a particular boy might be 'paired up' with 8 different possible girls.

     The next of 8 possible boys might be paired up with 8 diff. girls, 

...altogether, 8 times 8 = 64 possible pairings of mixed genders.