Question

If n is an integer of the sum of all even multiples of 15 between 295 and 615 , what is greast prime factor of n

Answer 1

The smallest even multiple of 15 between 295 and 615 is 15(20) = 300, and the largest is 15(40) = 600. Therefore, k = 300 + 330 + 360 + … + 600 = (300 + 600)/2 x 11 = 450 x 11 = 45 x 10 x 11 = 3^2 x 5 x 2 x 5 x 11. So the largest prime factor of k is 11.

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