Average cost of water

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Average cost of water

by hai1 » Mon Mar 08, 2010 6:15 am
The total cost of water for one year in Community Z of 120,000 homes is $75,000. If the cost were to increase to $80,000 for the community, by approximately what percent would the average cost of water increase for each household in Community Z ?

a. 70% b. 13% c. 7% d. 5% e. 1.3%

OA: c


My approach: Increase in cost of water for community= $5,000

Average cost of water increase for each household= 5,000/120,000=1/24 ~ 4%

Where am I going wrong in understanding the question?
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by dtweah » Mon Mar 08, 2010 6:26 am
hai1 wrote:The total cost of water for one year in Community Z of 120,000 homes is $75,000. If the cost were to increase to $80,000 for the community, by approximately what percent would the average cost of water increase for each household in Community Z ?

a. 70% b. 13% c. 7% d. 5% e. 1.3%

OA: c


My approach: Increase in cost of water for community= $5,000

Average cost of water increase for each household= 5,000/120,000=1/24 ~ 4%

Where am I going wrong in understanding the question?

Ave = 750000/120000 = 5/8

New Ave 80000/120000= 2/3

Percent inc is ( 2/3 - 5/8)/5/8 = 1/15 ~ 7%