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# M60-03

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6811
GMAT 1: 760 Q51 V42
GPA: 3.82

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11 Jun 2018, 01:26
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100% (01:00) correct 0% (00:00) wrong based on 3 sessions

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The cost, $$c$$ and the revenue, $$r$$ are related via the equation $$c =ar+b$$. By how much is the cost increased if the revenue is increased by $$10? (1)$$a=0.5$$(2)$$b=5$_________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 6811
GMAT 1: 760 Q51 V42
GPA: 3.82

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11 Jun 2018, 01:26
Official Solution:

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

The first step of the VA (Variable Approach) method is to modify the original condition and the question, and then recheck the question.

The equation $$c = ar + b$$ tells us that the cost is increases by $a when the revenue is increases by 1 dollar. It follows that the cost is increases by 10a when the revenue is increases by 10 dollars. So, the question is asking for the value of a. The answer is A. Answer: A _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$149 for 3 month Online Course"
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Intern
Joined: 14 Jun 2018
Posts: 47
Location: India

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13 Sep 2018, 04:02
MathRevolution wrote:
The cost, $$c$$ and the revenue, $$r$$ are related via the equation $$c =ar+b$$. By how much is the cost increased if the revenue is increased by $$10? (1)$$a=0.5$$(2)$$b=5$hello, Is there any simpler approach to this question? It would be of great help in understanding. thank you. Intern Joined: 02 Jul 2018 Posts: 4 Re: M60-03 [#permalink] ### Show Tags 29 Sep 2018, 16:50 1 Shri15kumar wrote: MathRevolution wrote: The cost, $$c$$ and the revenue, $$r$$ are related via the equation $$c =ar+b$$. By how much is the cost increased if the revenue is increased by $$10? (1)$$a=0.5$$(2)$$b=5$

hello,
Is there any simpler approach to this question? It would be of great help in understanding. thank you.

Given equation. C1 = ar + b
when revenue increases by $10, C2 = a(r+10)+b => C2=ar+10a+b Need to find cost increase. C2-C1= 10a A gives exactly that. Intern Joined: 08 Nov 2018 Posts: 3 Re M60-03 [#permalink] ### Show Tags 13 Nov 2018, 00:24 I think this the explanation isn't clear enough, please elaborate. Intern Joined: 15 Jan 2019 Posts: 3 M60-03 [#permalink] ### Show Tags 15 Jan 2019, 10:31 Given equation. C1 = ar + b when revenue increases by$10, C2 = a(r+10)+b => C2=ar+10a+b
Need to find cost increase. C2-C1= 10a
option a gives us the value of a while option b gives value of b
as c2 - c1 =10a we want the value of a
this is given by option a as a=0.5
hence c2-c1=0.5*10=5
hence
option b giving us the value of b is not of any use
M60-03 &nbs [#permalink] 15 Jan 2019, 10:31
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# M60-03

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