28) The following 7 numbers are given: 2, 3, 5, 7, 11, 13, 17. Calling a product “quaternary” if it has any 4 of these numbers, how many different, odd, quaternary products can be created?
We need to select 4 of these numbers such that the product is odd. This means we cannot select 2. We can select any 4 numbers from the leftover 6 numbers and their product will be quaternary.
How do you select 4 out of given 6 distinct objects? 6C4 = 15
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