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Recent problems solved by 'lar'

lar answered: 3 problems

Human-and-algebraic-language/381751: The sum of the digits of a certain two-digit number is 7. Reversing its digits increases the number by 9. what are the two equations?

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Answer 270754 by lar(3) on 2010-12-06 16:13:33 (Show Source):

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Let the digits of the number be x and y.
So the number is xy (note: this does not mean x times y).
x+y=7 and yx=xy+9
In order for yx to equal xy+9, x=y-1.
Now we have the two equations x+y=7 and x=y-1.
x+y=7 -> x=7-y
y-1=7-y
2y=8
y=4
Plug that into one of the original equations: x+4=7
x=3
The number is 34.

Linear_Equations_And_Systems_Word_Problems/381739: One cellular phone carrier charges $26.50 a month plus $.15 a minute for local calls. Another carrier charges $14.50 a month and $.25 a minute for local calls. For how many minutes is the cost of the plans the same?
1 solutions

Answer 270752 by lar(3) on 2010-12-06 16:10:01 (Show Source):

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26.50+t*0.15=14.50+t*0.25
t*0.1=12
t=120 mins

Distributive-associative-commutative-properties/381735: If 8 = x and x = y, then 8 = y is an example of which algebraic property?
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Answer 270750 by lar(3) on 2010-12-06 16:07:41 (Show Source):

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Transitive property

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Recent problems solved by 'lar'