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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
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The ratio of a to b to c is 2 to 3 to 4, and a, b, c are positive inte
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29 Jun 2016, 19:23
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The ratio of a to b to c is 2 to 3 to 4, and a, b, c are positive integers. If the average (arithmetic mean) of them is 18, what is the value of a? A. 3 B. 6 C. 9 D. 12 E. 15 *An answer will be posted in 2 days.
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Re: The ratio of a to b to c is 2 to 3 to 4, and a, b, c are positive inte
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29 Jun 2016, 20:34
(2+3+4)x =18*3 x=6 =>a=2x=2*6=12 Sent from my HTC Desire 816G dual sim using GMAT Club Forum mobile app



Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 9146
GPA: 3.82

Re: The ratio of a to b to c is 2 to 3 to 4, and a, b, c are positive inte
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03 Jul 2016, 04:42
a=2k, b=3k, c=4k, a+b+c=2k+3k+4k=(18)(3), 9k=18(3), k=6. Therefore, a=2k=2(6)=12, and the correct answer is D.
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Re: The ratio of a to b to c is 2 to 3 to 4, and a, b, c are positive inte
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03 Jul 2016, 05:02
D. 12 simply 3x will be the AM X=6 a=2x=12 Sent from my iPhone using GMAT Club Forum mobile app



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Re: The ratio of a to b to c is 2 to 3 to 4, and a, b, c are positive inte
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03 Jul 2016, 05:52
MathRevolution wrote: The ratio of a to b to c is 2 to 3 to 4, and a, b, c are positive integers. If the average (arithmetic mean) of them is 18, what is the value of a? A. 3 B. 6 C. 9 D. 12 E. 15
*An answer will be posted in 2 days. Plugging in Answer Choice worked for me Here given a:b:c=2:3:4 ,So a:b:c=1:\(\frac{3}{2}\):2 Now by putting value of a=12 on the ratio we can find that only answer choice D matched with a:b:c=12:18:24 ,arithmetic mean of them is \(\frac{12+18+24}{3}\)=18 Correct Answer D



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Re: The ratio of a to b to c is 2 to 3 to 4, and a, b, c are positive inte
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03 Jul 2016, 06:33
If a list of numbers is 'evenly spaced out,' then the average equals the median. (e.g. in the list {7, 14, 21, 28, 25}, 21 is immediately apparent as the average because each term is separated from the preceding term by the same number)
In this question, a, b and c are evenly spaced out, so we know that b is the average. Therefore b's real value is 18. this means our multiplier is 6. So a is 2*6=12.




Re: The ratio of a to b to c is 2 to 3 to 4, and a, b, c are positive inte
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03 Jul 2016, 06:33




