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DS Question on lcm and GCF

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DS Question on lcm and GCF

by dinesh19aug » Tue Aug 03, 2010 8:44 pm
What is the lcm of a and b?

1) GCF = 15
2) a=30 and a>b

I approached the problem with formula: GCF * LCM = a*b

Stmt 1 : LCM * 15 = a*b
Stmt 2: lcm *gcf = 30 * b

Combining: lcm *15 = 30 * b Still INSUFF

Hence I chose E.

OA = C
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Source: — Data Sufficiency |
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by sindhu b » Tue Aug 03, 2010 9:36 pm
IMO C

GCF of a and b is 15 it means both hav to be multiples of 15

and option B says a=30 and a>b so the mutiples of 15 <30 is only 15 and hence b =15 from which u

can determine the LCM
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by dinesh19aug » Tue Aug 03, 2010 10:04 pm
Got It Thanks.
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by selango » Tue Aug 03, 2010 10:37 pm
stmt1,

GCF=15

a=15*x

b=15*y

we don't know value of x and y.

Insuff

stmt2,

a=30,a>b

we don't know value of b.

Insuff

Combining 1 and 2,

a=30

So a=30=15*2

a>b-->b<30

Only one multiple of 15 (15*1)is available which is less than 30.

b=30=15*1

LCM(15,30)=30

Suff

Pick C
--Anand--
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