SOLUTION: How many terms of the sequence { } � , 18 , 13 , 8 must be taken for the series to be 426?

Question 1085414: How many terms of the sequence { } � , 18 , 13 , 8 must be taken for the series to be 426?
Answer by ikleyn(52788) (Show Source): You can put this solution on YOUR website!
.
HINT.

Write the sequence in the reversed order 

8, 13, 18 . . . 

to facilitate answering.



Use the formula for the sum of the first n terms of an AP.


Your first term is 8, and your common difference is 5.


The rest is arithmetic.

See introductory lessons on arithmetic progressions in this site:
    - Arithmetic progressions
    - The proofs of the formulas for arithmetic progressions
    - Problems on arithmetic progressions
    - Word problems on arithmetic progressions

Also, you have this free of charge online textbook in ALGEBRA-II in this site
    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Arithmetic progressions".

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