posted by Eryea on .
Find the sum of the 25th term to 50th term of the arithmetic progression 28,23,18, ...
You have an AS where a=28 and d= -5
Find the sum of the first 50 terms using your formula, and then the sum of the first 24 terms.
Subtract the two.
(you should get 7525 - 2052 = 5473 )
The progression lists stops on the downtown 1 train in New York. The next number in the sequence is 14, but that's the last numeric stop.
Try a real New York high school exam question: Complete the progression: