Kenneth S. answered • 02/20/18

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(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.