SOLUTION: The charge for 1 unit of electricity is increased from 6 cents to 6.25 cents. If a household reduces its consumption by 1.6%, by what percentage will his electricity bill increase?

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Question 475484: The charge for 1 unit of electricity is increased from 6 cents to 6.25 cents. If a household reduces its consumption by 1.6%, by what percentage will his electricity bill increase?
By what percentage does a household need to reduce its consumption in order that the electricity bill remains unchanged?

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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The charge for 1 unit of electricity is increased from 6 cents to 6.25 cents.
If a household reduces its consumption by 1.6%, by what percentage will his electricity bill increase?
:
Assuming they use 1000 kwh at the old rate: 1000 * .06 = $60.00
;
If they reduce their usage by 1.6%: 1000 - .016(1000) = 984 kwh * .0625 = $61.50
The bill increases by $1.50.
Find the percent increase of the their bill 1.50%2F60 * 100 = 2.5%
:
:
By what percentage does a household need to reduce its consumption in order that the electricity bill remains unchanged?
:
Let r = % (in decimals) reduction necessary to make the bill remain the same at the new rate
.0625(1000 - 1000r) = $60
62.5 - 62.5r = 60
-62.5r = 60 - 62.5
-62.5r = -2.5
r = 2.5%2F62.5
r = .04 * 100 = 4% reduction in usage for it to remain the same
;
:
See if this true
1000 - .04(1000) = 960 * .0625 = $60