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LCM of fraction

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LCM of fraction

by ayushiiitm » Sat Jul 17, 2010 11:56 am
Given the fraction a/b, if a and b are positive integers, what is the value of b?

1) The least common denominator of a/b and 1/4 is 12?

2)a=5



Got this question on Knewton diagnostic test

I want to know, what information can we decipher from stem (1)

What is the formula for LCM of fractions?

OA later
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by debmalya_dutta » Sat Jul 17, 2010 12:36 pm
Statement 1 says "The least common denominator of a/b and 1/4 is 12"
=> l.c.m of b & 4 is 12
=> b can be 3, 12.....
hence insufficient

From statement 2 , a= 5...again insufficient

Both together is also insufficient

Is the answer E?
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by ayushiiitm » Sat Jul 17, 2010 12:40 pm
BUlls Eye :)

OA is E

Can u explain

=> l.c.m of b & 4 is 12
=> b can be 3, 12.....
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by gmatruler » Sat Jul 17, 2010 1:26 pm
The least common denominator of 2 fractions is the Least Common Multiple (LCM) of the denominators. So statement 1 tells us that the LCM of 4 and b is 12.
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by debmalya_dutta » Sat Jul 17, 2010 5:15 pm
ayushiiitm wrote:BUlls Eye :)

OA is E

Can u explain

=> l.c.m of b & 4 is 12
=> b can be 3, 12.....
Ayush-
if you take the LCM of 3 and 4 , it is 12
if you take the LCM of 6 and 4 , it is 12
if you take the LCM of 12 and 4 , it is 12

SO, if your question was how do I know that b assumes the above mentioned values .... just knew it ... sorry couldnt be of much help...
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by ayushiiitm » Sun Jul 18, 2010 10:12 am
I got it , thanks everybody
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