.
I just answered this question once, but it came again.
Ok, I will explain one more time.
Mailing 1 2 3 4 5 6
number of letters 1 3 3^2 3^3 3^4 3^5
sent
The total = 1 + 3 + 3^2 + 3^3 + 3^4 + 3^5.
Use your calculator.
Or, alternatively, use the formula for the sum of the first 6 terms of an geometric progression
with the first term of 1 and the common ratio of 3.
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To learn the formula for summing, see introductory lessons on geometric progressions
- Geometric progressions
- The proofs of the formulas for geometric progressions
- Problems on geometric progressions
- Word problems on geometric progressions
in this site.
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
"Geometric progressions".
Save the link to this textbook together with its description
Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson
into your archive and use when it is needed.
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