Question 588547: 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?
Found 2 solutions by Theo, ikleyn:
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! 90 foot tower would cost as follows:
cost for first 10 feet = $100.
cost for additional 80 feet = 8*25 = $200.
total cost would be $300.
Answer by ikleyn(52908)  (Show Source):
You can put this solution on YOUR website! .
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?
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Tutor @Theo incorrectly read/interpreted the problem and produced incorrect calculations.
I came to provide a correct solution.
We have here an arithmetic progression 100, 125, 150, . . . of 9 terms,
that correspond to the heights 10, 20, 30, . . . , 90 feet.
And they want you find the sum of this progression.
Use the formula for the sum of an arithmetic progression
S =  .
In your case, n = 9,  =  +  = 100 + 8*25 = 300.
Therefore, the total sum of 9 terms is
S =  = 200*9 = 1800 dollars. <<<---=== ANSWER
Solved correctly.
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