If x is a sum of all even integers on the interval 13...55 and y is their number, what is the GCD (x, y)? Pick one
A) 1
B) 21
C) 26
D) 52
E) 1014
x = 14 + 16 + ... + 54 = (largest + smallest)/2 *(# of terms) = (14 + 54)/2*21= 34*21.   GCD of 21 and 34*21 is 21   Answer: 21.
<result>B</result>
If x is a sum of all even integers on the interval 13...55 and y is their number, what is the GCD (x, y)?