If integer k is equal to the sum of all even multiples of 35 between 280 and 630, what is the greatest prime factor of k?
Choices:
A) 5
B) 7
C) 11
D) 13
E) 11*455
if we break down what the stem is asking what is the sum of all mult of 30 between 300 and 600.   using arithmetic progression to find n : 630 =280+ (n - 1) 35   350+ 35 = 35n   385 = 35n =&gt; n = 11   the sum would be: 11* mean   mean = [630 + 280] / 2 = 455   11*455 =   11*455
<result>E</result>
If integer k is equal to the sum of all even multiples of 35 between 280 and 630, what is the greatest prime factor of k?