SOLUTION: Find the sume of this series. 28+35+42+49+......728. I know this is 7 added each time. But stuck on the equation to figure.

Algebra ->  Sequences-and-series -> SOLUTION: Find the sume of this series. 28+35+42+49+......728. I know this is 7 added each time. But stuck on the equation to figure.       Log On


   

Question 50375: Find the sume of this series.
28+35+42+49+......728.
I know this is 7 added each time. But stuck on the equation to figure.
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
28+35+42+49+......728.

The sum is the average of the 1st and last terms times the number of terms.
S=(1/2)n(1st + last)
Need to find number of terms, as follows:
728-28=700
700/7 = 100
So, 728 is the 100th term.
S=1/2(100)(28+728)
S=50(756)
S=37,800
Cheers,
Stan H.