<PRE><B>Question 772070</B>
Hi,

This is arithmetic sequence because the common difference:

 d = 28 - 25 = 31- 28 =...= 3

Apply the formula

a(n) = a(1) + (n- 1)d

100 = 25 + (n - 1)3

100 = 25 + 3n - 3

3n - 3 = 75

3n = 78

n = 26

So we have 26 terms totally

To find the sum, apply the formula:

S(n) = n(a(1) + a(n))/2
     = (26/2)( 25 + 100)
     = (13)(125)
     = 1625

Hope it helps you!

John10 (john100185@yahoo.com)</PRE>