SOLUTION: A person hired a firm to build a CB radio tower. The firm charges $100 for labor for the first 10 feet. After that, the cost of the labor for each succeeding 10 feet is $25 more t

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Question 635275: A person hired a firm to build a CB radio tower. The firm charges $100 for labor for the first 10 feet. After that, the cost of the labor for each succeeding 10 feet is $25 more than the preceding 10 feet. That is, the next 10 feet will cost $125, the next 10 feet will cost $150, etc. How much will it cost to build a 90 foot tower?
I was able to come up with the answer as $300 but don't understand how to put it in its proper formula and steps to how I came up with the answer
Answer by solver91311(24713) (Show Source):
You can put this solution on YOUR website!

Boy are you in for some sticker shock. $300 is what it costs you for the LAST 10 foot section, but doesn't help you pay for the previous eight 10-foot sections.

Each 10 foot section, and we'll number them from 0 through 8, costs you $100 plus $25 times the number of the section.

So you have sections times $100 plus , which can be written . But the sum of a series of integers can be calculated using:

And so your total is

Do the arithmetic.

John

My calculator said it, I believe it, that settles it