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# M23-09

Author Message
Manager
Joined: 01 May 2012
Posts: 57
GPA: 1

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08 Jun 2012, 00:54
1
KUDOS
Okay folks, this is a quiz question from the "hard" section of the GMAT club quizzes.

When I encountered this question, I didn't even bother doing it - since I don't have a goddamn calculator with me!
-----------------------------------------
A plane flying against the wind covers the 900-kilometer distance between two aerodromes in 2 hours. The same plane flying with the wind covers the same distance in 1 hour and 48 minutes. If the speed of the wind is constant, what is the speed of the wind?
18 kmh
20 kmh
22 kmh
25 kmh
27 kmh
Mark as a guess Hide Answer

--------------------------------------------

So, I start by doing this :
set plane speed as V, wind speed S
900 / (V-S) = 120
900 / (V+S) = 108

I find the numbers very bad to deal with. Or, I could make 1 H 48 M something better... 1 + 48/60, that is 1.8

So 2 (v-s) =900 1.8(v+s) = 900

v-s = 450 v+s = ??
2s= 900/1.8 - 900/2
s= (900/1.8- 900/2) /2

See, how the hell do I untangle the 900/1.8 without a calculator? Is this even common on GMAT that they deliberately test your manual calculation skills? I find this as frustrating as calculating, say 9/1.7+2.3+17/0.3 - it could take a couple of minutes
Intern
Status: ISB 14...:)
Joined: 26 May 2012
Posts: 30
Location: India
Concentration: Strategy
Schools: ISB '14 (A)
GMAT 1: 750 Q51 V39
GPA: 3.62
WE: Engineering (Energy and Utilities)

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08 Jun 2012, 03:35
1
KUDOS
I dont think you need a calculator for doing 900/1.8

900/1.8 = 9000/18

Just divide numerator and denominator with 9.

so it become 1000/2 = 500

it takes only a few seconds.
Manager
Joined: 01 May 2012
Posts: 57
GPA: 1

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08 Jun 2012, 03:40
1
KUDOS
yeah, right. Probably I wasn't doing "mental math" right. too used to calculators!
Re: M23-09   [#permalink] 08 Jun 2012, 03:40
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# M23-09

Moderator: Bunuel

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