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# The cost, c and the revenue, r are related via the equation

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 8017
GMAT 1: 760 Q51 V42
GPA: 3.82
The cost, c and the revenue, r are related via the equation  [#permalink]

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11 Jan 2018, 01:42
00:00

Difficulty:

45% (medium)

Question Stats:

59% (01:19) correct 41% (01:32) wrong based on 72 sessions

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[GMAT math practice question]

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$79 for 1 month Online Course"
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Math Expert
Joined: 02 Aug 2009
Posts: 7978
Re: The cost, c and the revenue, r are related via the equation  [#permalink]

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11 Jan 2018, 04:40
1
MathRevolution wrote:
[GMAT math practice question]

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 C=ar+b... If revenue increases by 10.. $$c_1=a(r+10)+b= ar+10a+b$$.. Increase is 10a, so u require value of only a.. Statement I gives value of a.. Increase=10*0.5=5 Suff A _________________ Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 8017 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: The cost, c and the revenue, r are related via the equation [#permalink] ### Show Tags 14 Jan 2018, 18:26 => 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. It follows that the cost is increases by$10a when the revenue is increases by $10. 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$79 for 1 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"
Re: The cost, c and the revenue, r are related via the equation   [#permalink] 14 Jan 2018, 18:26
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