How many positive integers can be expressed as a product of two or more of the primes numbers 5,7,11 and 13 if no one product is to include the same factor more than once?
A) 8 b) 9 c) 10 d) 11 e) 12
I got E as the answer ... don't have the OA to this one ... Please show your approach to solve and help to confirm ...
I think this is a simple case of permutations. So for this P(4,2) = 4!/(4-2)! = 24/2 = 12.
Just a few electrons short of a full cloud...