Mathur S.

asked • 11/30/17

Find the sum of ap 7+10.5+14+...+84

Find the sum of ap
 

1 Expert Answer

By:

Andrew M. answered • 11/30/17

Tutor
New to Wyzant

Mathematics - Algebra a Specialty / F.I.T. Grad - B.S. w/Honors

See tutors like this
See tutors like this
Common difference is 3.5
7 + 3.5 = 10.5
10.5 + 3.5 = 14
.
.
.
84
 
7 + 3.5x = 84
3.5x = 77
x = 22
 
Total terms in the series is n = x+1 so n=23 terms
  
Sum = (n/2)(a1+an) = (23/2)(7+84) = (23/2)(91) = 1046.5
Upvote • 0 Downvote
More
Report

Andrew M.

To find n the general formula is
a1 + (n-1)d = an
 
7 + (n-1)(3.5) = 84
7 + 3.5n - 3.5 = 84
3.5n + 3.5 = 84
3.5n = 80.5
n = 23 terms in sequence.  :-)
Report

11/30/17

Still looking for help? Get the right answer, fast.

Ask a question for free

Get a free answer to a quick problem.
Most questions answered within 4 hours.

OR

Find an Online Tutor Now

Choose an expert and meet online. No packages or subscriptions, pay only for the time you need.