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Manager
Joined: 04 Dec 2008
Posts: 109
Followers: 1

Kudos [?]: 75 [0], given: 2

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Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
If c + d = 11 and c and d are positive integers, which of the following is a possible value for
5c + 8d?

(A) 55
(B) 61
(C) 69
(D) 83
(E) 88

Is there any shortcut to this?
SVP
Joined: 07 Nov 2007
Posts: 1828
Location: New York
Followers: 29

Kudos [?]: 532 [1] , given: 5

1
KUDOS
joyseychow wrote:
If c + d = 11 and c and d are positive integers, which of the following is a possible value for
5c + 8d?

(A) 55
(B) 61
(C) 69
(D) 83
(E) 88

Is there any shortcut to this?

5c + 8d = 5c+5d+ 3d = 5*11+3d = 55+3d
Here d must any integers from 1 to 10

C --> 55+14 ( 14 is not multiple of 3 ) --> out
D --> 55+28 ( not multiple of 3) out
E --> 55+33 (d must be between 1 and 10 .. here it is 11) -->out

A--> out
B --> 55 +3*2 = 61 (Potential answer)
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CEO
Joined: 17 Nov 2007
Posts: 3578
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
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Kudos [?]: 2117 [0], given: 359

Expert's post

1) let's c=10 and d=1 --> 5*c + 8*d = 58
2) When we decrease c by 1 increasing d by 1, we increase 5*c + 8*d by (+8-5) = 3.
3) Let's add 3n to 58: 58, 61, 64, 67, 70, 73, 76, 79, 81, 84.
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Senior Manager
Joined: 08 Jan 2009
Posts: 329
Followers: 2

Kudos [?]: 85 [0], given: 5

hi X2suresh,

Why d has to b/w one to 10? d is postive integer so i can be any value > 0.

The problem i think is if u take d = 11 then u will get c = 0. Which is not a positive integer so E is out.

Please correct me if i am wrong.
SVP
Joined: 07 Nov 2007
Posts: 1828
Location: New York
Followers: 29

Kudos [?]: 532 [0], given: 5

tkarthi4u wrote:
hi X2suresh,

Why d has to b/w one to 10? d is postive integer so i can be any value > 0.

The problem i think is if u take d = 11 then u will get c = 0. Which is not a positive integer so E is out.

Please correct me if i am wrong.

Question stem says c and d are positive integers

and c+d = 11 ..
minmum value of c=1 c can't be equal to zero. ( Zero is neighter +Ve nor -ve)
so max value of d = 10
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Senior Manager
Joined: 08 Jan 2009
Posts: 329
Followers: 2

Kudos [?]: 85 [0], given: 5

Thanks X2suresh.

some times it take the brain a little more help to understand.
Manager
Joined: 11 Aug 2008
Posts: 162
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Kudos [?]: 37 [0], given: 8

5c+8d=5(c+d)+3d=55+3d=61 => d=2 hence B
Manager
Joined: 12 Oct 2009
Posts: 115
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Kudos [?]: 29 [0], given: 3

ngoctraiden1905 wrote:
5c+8d=5(c+d)+3d=55+3d=61 => d=2 hence B

sorry but the above equation seems to find the value of d rather than finding a possible value for the expression.
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