Question 1197648: In preparing a bid for constructing a new building,a contractor determines that the foundation and basement will cost $605000 and the first floor will cost $360000.Each floor above the first will cost $15000 more than the one below it.How much will the building cost if it is to be 18 floors high?
Thank you.
Found 2 solutions by ewatrrr, MathTherapy:
Answer by ewatrrr(24785)   (Show Source):
You can put this solution on YOUR website!
Hi
How much will the building cost if it is to be 18 floors high?
$360,000 + Cost of 18 Floors:
cost of the 18 Floors:
S = (n/2)(2a + (n-1)d) a = 150,000 n = 18, d = 15,000
S = (18/2)(2(150,000) + (18-1)15000)= $4,995,000
$360,000 + $4,995,000 = $5,355,000
Wish You the Best in your Studies.
Answer by MathTherapy(10552)  (Show Source):
You can put this solution on YOUR website! In preparing a bid for constructing a new building,a contractor determines that the foundation and basement will cost $605000 and the first floor will cost $360000.Each floor above the first will cost $15000 more than the one below it.How much will the building cost if it is to be 18 floors high?
Thank you.
To determine the cost of the 1st floor up to the 18th, we use the formula
for the SUM of an AP: 
 , with n being 18, a1, 360,000, and d, 15,000
S18 = 9[720,000 + 17(15,000)]
= 9(720,000 + 255,000)
= 9(975,000)
= 8,775,000
With cost of the 1st floor up to the 18th being $8,775,000, and cost of foundation and basement, $605,000,
ENTIRE building then costs: 8,775,000 + $605,000 = $9,380,000
BTW, solution by tutor @EWATRRR is INCORRECT!
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