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# If the average (arithmetic mean) of 3 integers x, y, z is 10, what is

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Math Revolution GMAT Instructor
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If the average (arithmetic mean) of 3 integers x, y, z is 10, what is  [#permalink]

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14 Aug 2018, 17:45
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25% (medium)

Question Stats:

72% (00:50) correct 28% (01:00) wrong based on 47 sessions

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[Math Revolution GMAT math practice question]

If the average (arithmetic mean) of 3 integers x, y, z is 10, what is the value of z?

1) x=1
2) x=5-y

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MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
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"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" Math Expert Joined: 02 Aug 2009 Posts: 7764 Re: If the average (arithmetic mean) of 3 integers x, y, z is 10, what is [#permalink] ### Show Tags 14 Aug 2018, 19:57 MathRevolution wrote: [Math Revolution GMAT math practice question] If the average (arithmetic mean) of 3 integers x, y, z is 10, what is the value of z? 1) x=1 2) x=5-y So x+y+z=30......z=? 1) x=1.. y+z=29... Insufficient 2) x=5-y x+y=5.. So z=30-5=25 Sufficient B _________________ Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 7609 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: If the average (arithmetic mean) of 3 integers x, y, z is 10, what is [#permalink] ### Show Tags 15 Aug 2018, 07:45 => 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. We then recheck the question. The original condition gives $$\frac{( x + y + z )}{3} = 10$$ or $$x + y + z = 30$$. Rearranging yields $$z = 30 – ( x + y ).$$ Condition 2) gives $$x + y = 5$$, so condition 2) is sufficient . Condition 1) is not sufficient since it gives no information about the value of y. Therefore, B is the answer. Answer: B _________________ 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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Re: If the average (arithmetic mean) of 3 integers x, y, z is 10, what is  [#permalink]

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15 Aug 2018, 09:26
Given: $$\frac{x+y+z}{3}$$= 10; x+y+z=30

1) x=1. No inf of y. So z cannot be calculated.[Insuff]

2) x= 5-y; x+y=5; Put this value in original equation above. Value of z can be found [Suff]

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Re: If the average (arithmetic mean) of 3 integers x, y, z is 10, what is   [#permalink] 15 Aug 2018, 09:26
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