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Algebra - 3 pencils, 2 pencils and 3 pens, and1 pen

by Fred
(Saxaphaw)











































If 3 pencils cost $.72, and 2 pencils and 3 pens cost $.78, how much is 1 pen?

Comments for Algebra - 3 pencils, 2 pencils and 3 pens, and1 pen

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Jun 24, 2012
Calculate Cost of Pen
by: Staff


The answer:

x = cost of one pencil

y = cost of one pen


3 pencils cost $.72

3x = $.72


2 pencils and 3 pens cost $.78

2x + 3y = $0.78


Solve for x using the 1st equation

3x = $.72

3x / 3 = $.72 / 3

x * (3 / 3) = $.72 / 3

x * (1) = $.72 / 3

x = $.72 / 3

x = $ 0.24


Substitute 0.24 for x in the 2nd equation, and then solve for y:

2x + 3y = $0.78

2 * (0.24) + 3y = 0.78

0.48 + 3y = 0.78

0.48 + 3y - 0.48 = 0.78 - 0.48

0.48 - 0.48 + 3y = 0.78 - 0.48

0 + 3y = 0.78 - 0.48

3y = 0.78 - 0.48

3y = 0.30

3y / 3 = 0.30 / 3

y * (3 / 3) = 0.30 / 3

y * (1) = 0.30 / 3

y = 0.30 / 3

y = 0.10



>>> the final answer:

The cost of one pen = $0.10

---------------------------------------
Check the answer by substituting the values of x and y into the original equations:

x = $ 0.24

y = $0.10

3x = $.72

3 * (0.24) = .72

.72 = .72, OK



2x + 3y = $0.78

2 * 0.24 + 3 * 0.10 = 0.78

0.78 = 0.78, OK




Thanks for writing.

Staff
www.solving-math-problems.com


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