C,D & E are one digit number

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[email protected]: Junior | Next Rank: 30 Posts; Posts: 29; Joined: Tue Jan 08, 2008 1:42 pm

by [email protected] » Mon Dec 20, 2010 2:58 pm

If each of C,D,E are one digit number, what is the value of E?
1.C=1 & CDE=24
2.D/C=4 & D/E=2/3.

Thanks
Archit

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Source: Beat The GMAT — Data Sufficiency | Mon Dec 20, 2010 2:58 pm

Night reader: Legendary Member; Posts: 1337; Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members; Thanked: 127 times

by Night reader » Mon Dec 20, 2010 3:26 pm

[email protected] wrote:If each of C,D,E are one digit number, what is the value of E?
1.C=1 & CDE=24
2.D/C=4 & D/E=2/3.

Thanks
Archit

IOM C

C,D,E are one digit numbers, find E

st(1) C=1, DE=24 D and E belong to {3,4,6,8} => hence multiple values for D and E, Not sufficient
st(2) D/C=4 & D/E=2/3 (also 4/6, keep for note') => C/D=1/4 & E/D=3/2 => C/E=1/6 => C/D/E=1:4:6 => we are given only ratios, no single value or total value is known therefore Not sufficient

Combining st(1&2) D=4 and DE=24, therefore E=6, >>>> test C/D/E=1:4:6, Sufficient

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clock60: Legendary Member; Posts: 759; Joined: Mon Apr 26, 2010 10:15 amFollowed by: 3 members; Thanked: 85 times

by clock60 » Mon Dec 20, 2010 3:40 pm

my answer is B
(1) st clearly insuff
(2) d/c=4 we have two pairs for d,c
d=4,c=1, and d=8,c=2

for d/e=2/3 options are following
e=3,d=2 or e=6,d=4, or e=9,d=6

here we have matched values only in one case e=6. d=4.c=1

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Night reader: Legendary Member; Posts: 1337; Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members; Thanked: 127 times

by Night reader » Mon Dec 20, 2010 4:12 pm

clock60 wrote:my answer is B
(1) st clearly insuff
(2) d/c=4 we have two pairs for d,c
d=4,c=1, and d=8,c=2

for d/e=2/3 options are following
e=3,d=2 or e=6,d=4, or e=9,d=6

here we have matched values only in one case e=6. d=4.c=1

clock you select the set e=6,d=4 arbitrarily => we don't know what's c-? you could also select e=-3,d=-2 for d or all other opposite pairs possible, we need c at the end point. your's B is based on assumption +ve for all numbers
st(1) suggests c=1 and leads to solution.

my final thought is C

what's OA?

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[email protected]: Junior | Next Rank: 30 Posts; Posts: 29; Joined: Tue Jan 08, 2008 1:42 pm

by [email protected] » Mon Dec 20, 2010 4:27 pm

The official answer( as per Grockit) is B. I think it should be C

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Night reader: Legendary Member; Posts: 1337; Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members; Thanked: 127 times

by Night reader » Mon Dec 20, 2010 4:51 pm

[email protected] wrote:The official answer( as per Grockit) is B. I think it should be C

archit, the BTG mate has posted Grockit question recently and the answer was not the same our favorite expert, Rahul provided

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Rahul@gurome: GMAT Instructor; Posts: 1179; Joined: Sun Apr 11, 2010 9:07 pmFollowed by: 88 members; Location: Milpitas, CA; Thanked: 447 times

by Rahul@gurome » Mon Dec 20, 2010 7:57 pm

[email protected] wrote:If each of C,D,E are one digit number, what is the value of E?
1.C=1 & CDE=24
2.D/C=4 & D/E=2/3.

Statement 1: C = 1 and CDE = 24
Thus DE = 24 = 3*8 = 4*6
Possible values of (D, E) are: (3, 8), (4, 6), (6, 4) and (8, 3)

Not sufficient

Statement 2: D/C = 4 and D/E = 2/3
Possible values of (C, D) are: (1, 4) and (2, 8)
Possible values of (D, E) are: (2, 3), (4, 6) and (6, 9)
As values of D must be same in both cases, only possible values of (C, D, E) are: (1, 4, 6)

Sufficient

The correct answer is B.

Note: The above solution is based on the assumption that the "one digit numbers" are positive. If negative numbers are considered then one more set of values for (C, D, E) is possible for statement 2, which is (-1, -4, -6). And thus C should be the answer.

Rahul Lakhani
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https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
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[email protected]: Junior | Next Rank: 30 Posts; Posts: 29; Joined: Tue Jan 08, 2008 1:42 pm

by [email protected] » Mon Dec 20, 2010 8:31 pm

Thanks Rahul.

I appreciate it.

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Night reader: Legendary Member; Posts: 1337; Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members; Thanked: 127 times

by Night reader » Tue Dec 21, 2010 3:53 am

Rahul@gurome wrote:
[email protected] wrote:If each of C,D,E are one digit number, what is the value of E?
1.C=1 & CDE=24
2.D/C=4 & D/E=2/3.
Statement 1: C = 1 and CDE = 24
Thus DE = 24 = 3*8 = 4*6
Possible values of (D, E) are: (3, 8), (4, 6), (6, 4) and (8, 3)

Not sufficient

Statement 2: D/C = 4 and D/E = 2/3
Possible values of (C, D) are: (1, 4) and (2, 8)
Possible values of (D, E) are: (2, 3), (4, 6) and (6, 9)
As values of D must be same in both cases, only possible values of (C, D, E) are: (1, 4, 6)

Sufficient

The correct answer is B.

Note: The above solution is based on the assumption that the "one digit numbers" are positive. If negative numbers are considered then one more set of values for (C, D, E) is possible for statement 2, which is (-1, -4, -6). And thus C should be the answer.

the problem doesn't specify +ve for numbers, therefore I chose C. With B why don't we make other assumptions too and select D or A?

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by Rahul@gurome » Tue Dec 21, 2010 4:19 am

Night reader wrote:With B why don't we make other assumptions too and select D or A?

Because generally when some number is said as "n-digit number" we consider positive numbers only. For example there are various questions like:

"How many 2 digit numbers are there with different digits?"
- While solving this question we don't consider the negative numbers like -51 or -89 etc.

I agree that the numbers are "positive" should be mentioned for clarification, but it is a very common practice. Keep an eye for digits related combinatorics problems. You'll find that most of the time "positive" is not mentioned and all of us don't bother about it. I believe this question is also framed on the same common practice.

Rahul Lakhani
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)

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