Re: If P is the product of all of the positive multiples of 11
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05 Nov 2017, 06:28
The product of all the multiples of 11 below 100 would be 11*22*33*44*55*66*77*88*99 but it is quite long to compute the multiplication using the calculator and then looking for the prime factors.
Let's use a trick: since all the numbers are multiples of 11 we can factorize 11 from each term of the multiplication in order to get 11*(1*2*3*4*5*6*7*8*9).
Now, let's focus on those numbers of the multiplication which are prime numbers because they coincide with the prime factors of the number of interest. Thus, we have 2, 3, 5, 7 and 11.
Summing them we get 28 and answer B!