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Q. 50

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Precalculus Enhanced with Graphing Utilities
Found in: Page 102
Precalculus Enhanced with Graphing Utilities

Precalculus Enhanced with Graphing Utilities

Book edition 6th
Author(s) Sullivan
Pages 1200 pages
ISBN 9780321795465

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Short Answer

In March 2011, Nicor Gas had the following rate schedule for natural gas usage in single-family residences:

Monthly customer charge -$13.55

Distribution charge

First 20 therms-0.1473/therm

Next 30 therm -$0.0579/therm

Over 50 therm -$0.0519/therm

Gas supply charge-$0.51/therm

(a) What is the charge for using 40 therms in a month?

(b) What is the charge for using 150 therms in a month?

(c) Develop a model that gives the monthly charge C for x therms of gas.

(d) Graph the function found in part (c).

(a) The charge for using 40 therms in a month is $38.054

(b) The charge for using 150 therms in a month is $99.923

(c) The model that gives the monthly charge C for x therms of gas is C(x)=0.5619x+2.088,x>500.5679x+1.788,x50

(d) The graph of the function found in part (c) is:

See the step by step solution

Step by Step Solution

Part (a) Step 1. Given

Monthly customer charge-$13.55

First 20 therms-$0.1473/therm

Next 30 therms-$0.0579/therm

Over 50 therms-$0.0519/therm

Gas supply charge-$0.51/therm

Part (a) Step 2. Find the distribution charge and gas charge

The distribution charge for first 20 therms is

=0.1473×20=$2.946

The distribution charge for the next 20 therms is

=0.0579×20=$1.158

Gas charge for 40 therms =0.51×40

=$20.4

Part (a) Step 3. Add the terms found above.

Charge for using 40 therms in a month=13.55+2.946+1.158+20.4=$38.054

Part (b) Step 1. Find the distribution charge and gas charge

Referring to part (a), the distribution charge for using first 20 therms is $2.946

The distribution charge for the next 30 therms =0.0579×30

=$1.737

The distribution charge for next 100 therms,

=0.0519×100=$51.9

Gas charge for 150 therms =0.51×150

=$76.5

Part (b) Step 2. Find the total charge

Monthly service charge=$13.55

Total charge for using 150 therms is given by,

=13.55+2.946+1.737+5.19+76.5=$99.923

Part (c) Step 1. To find the charges for therms

Monthly charge =$13.55

Referring to part (a), (b), the distribution charge for 20 therms is $2.946 and the distribution charge for next 30 therm is $1.737

The distribution charge for next (x-50) therms is,

=0.0519(x-50)=0.0519x-2.595

The gas charge for x therms=0.51x

Part (c) Step 2. Find model C for x therms for x≥50

For x50 the total charge is given by

C(x)=2.946+1.737+0.0519x-2.595+0.51x =0.5619x+2.088

Part (c) Step 3. Find the model for x<50 

The total charge for x terms if x<50 is given by,

=0.0579(x-20)=0.0579x-1.158

Total charge for x thermsC(x)=2.946+0.0579x-1.158+0.51x =0.5679x+1.788

Part (d) Step 1. Graph the function in part (c)

Graph the function C(x)=0.5619x+2.088,x>500.5679x+1.788,x50

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