Posted by **ann** on Friday, April 13, 2012 at 11:40pm.

could you please show me how to do this problem?

ballfield costs 14,850,00 to build. the cost per city resident to build it will be based on last census. New census shows population increased by 2200 people, which reduced the cost per resident $75. what is the current population of the city?? thank you

- algebra -
**Reiny**, Friday, April 13, 2012 at 11:57pm
The way you grouped the cost by thousands, I think you left out a zero

is it 14 850 000 ?

let currect population be x

last year's population is x - 2200

currect cost per person = 14850000/x

last year's cost per person = 14850000/(x-2200)

14850000/(x-2200) - 14850000/x = 75

14850000x - 14850000(x-2) = 75x(x-2200)

75x^2 - 165000x - 14850000(2200) = 0

x^2 - 2200x = 435 600 000

x^2 - 2200x + 1210000 = 435 600 000 + 1 210 000

(x - 1100)^2 = 436 810 000

x - 1100 = 20900

x = 22 000

check:

current pop: = 22000

cost per person = 14850000/22000 = 675

last years' pop = 19800

cost per person = 14850000/19800 = 750

change = 750-675 = 75 , YEAHH!

- algebra -
**ann**, Saturday, April 14, 2012 at 1:02am
yes you were right about the zero. Thank you so much for showing me how to do it. ann

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