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by Night reader » Sun Oct 31, 2010 12:54 pm
replayyyy wrote:In the fraction x/y, where x and y are positive integers, what is the value of y?
(1) the least common denominator of x/y and 1/3 is 6
(2) x=1
Answer C

Basically, we need the least common denominator (LCD) for two fractions which is given, 6 and we have to assign the denominator for y which is factor of 6 with LCD for both fractions in mind. Within statement (1) LCD=6 we have the denominator of x/y which could be assigned as y=6

Then nominator, can not be 2, 3, or 6 it can not be 12 as well; it must be some value for us to keep the denominator y as 6. We have the statement (2) where x=1

Both statements satisfy.
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by Rahul@gurome » Sun Oct 31, 2010 7:40 pm
The lowest common denominator or least common denominator (abbreviated LCD) is the least common multiple of the denominators of a set of vulgar fractions. It is the smallest positive integer that is a multiple of the denominators. For instance, the LCD of 5/12 and 11/18 is 36 because the least common multiple of 12 and 18 is 36.

In the fraction x/y, where x and y are positive integers, what is the value of y?
(1) the least common denominator of x/y and 1/3 is 6
(2) x=1.

Consider first (1) alone.
Let x/y be 5/6 where x = 5 and y = 6. Here LCD is LCM of y = 6 and 3 which is 6.
Here we have that y = 6.
Next let x/y = 1/2 where x = 1 and y = 2. Here LCD is LCM of y = 2 and 3 which is also 6 but here y = 2.
So we do not get a definite value of y from (1) alone.
Or (1) alone is not sufficient.
Next consider (2) alone.
It says x = 1.
Obviously it is not sufficient because we cannot say anything about y from this.
Next combine both the statements together and check.
Again case (1) x = 1 and y = 2. So x/y is ½. LCD is again 6 and y = 2.
Case (2) x = 1 and y = 6. So x/y is 1/6. LCD is again 6 and y = 6.

Even after combining we are not getting a definite value of y.

The correct answer is E.
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by replayyyy » Mon Nov 01, 2010 12:30 am
Тhanks for the explanations. OA is E.
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by kapur.arnav » Mon Nov 01, 2010 9:50 am
Rahul@gurome wrote:The lowest common denominator or least common denominator (abbreviated LCD) is the least common multiple of the denominators of a set of vulgar fractions. It is the smallest positive integer that is a multiple of the denominators. For instance, the LCD of 5/12 and 11/18 is 36 because the least common multiple of 12 and 18 is 36.

In the fraction x/y, where x and y are positive integers, what is the value of y?
(1) the least common denominator of x/y and 1/3 is 6
(2) x=1.

Consider first (1) alone.
Let x/y be 5/6 where x = 5 and y = 6. Here LCD is LCM of y = 6 and 3 which is 6.
Here we have that y = 6.
Next let x/y = 1/2 where x = 1 and y = 2. Here LCD is LCM of y = 2 and 3 which is also 6 but here y = 2.
So we do not get a definite value of y from (1) alone.
Or (1) alone is not sufficient.
Next consider (2) alone.
It says x = 1.
Obviously it is not sufficient because we cannot say anything about y from this.
Next combine both the statements together and check.
Again case (1) x = 1 and y = 2. So x/y is ½. LCD is again 6 and y = 2.
Case (2) x = 1 and y = 6. So x/y is 1/6. LCD is again 6 and y = 6.

Even after combining we are not getting a definite value of y.

The correct answer is E.
The lowest common denominator or least common denominator (abbreviated LCD) is the least common multiple of the denominators of a set of vulgar fractions. It is the smallest positive integer that is a multiple of the denominators. For instance, the LCD of 5/12 and 11/18 is 36 because the least common multiple of 12 and 18 is 36.

Im not 100% clear on this... is this a rule!!!...
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by kapur.arnav » Mon Nov 01, 2010 9:54 am
kapur.arnav wrote:
Rahul@gurome wrote:The lowest common denominator or least common denominator (abbreviated LCD) is the least common multiple of the denominators of a set of vulgar fractions. It is the smallest positive integer that is a multiple of the denominators. For instance, the LCD of 5/12 and 11/18 is 36 because the least common multiple of 12 and 18 is 36.

In the fraction x/y, where x and y are positive integers, what is the value of y?
(1) the least common denominator of x/y and 1/3 is 6
(2) x=1.

Consider first (1) alone.
Let x/y be 5/6 where x = 5 and y = 6. Here LCD is LCM of y = 6 and 3 which is 6.
Here we have that y = 6.
Next let x/y = 1/2 where x = 1 and y = 2. Here LCD is LCM of y = 2 and 3 which is also 6 but here y = 2.
So we do not get a definite value of y from (1) alone.
Or (1) alone is not sufficient.
Next consider (2) alone.
It says x = 1.
Obviously it is not sufficient because we cannot say anything about y from this.
Next combine both the statements together and check.
Again case (1) x = 1 and y = 2. So x/y is ½. LCD is again 6 and y = 2.
Case (2) x = 1 and y = 6. So x/y is 1/6. LCD is again 6 and y = 6.

Even after combining we are not getting a definite value of y.

The correct answer is E.
The lowest common denominator or least common denominator (abbreviated LCD) is the least common multiple of the denominators of a set of vulgar fractions. It is the smallest positive integer that is a multiple of the denominators. For instance, the LCD of 5/12 and 11/18 is 36 because the least common multiple of 12 and 18 is 36.

Im not 100% clear on this... is this a rule!!!...
ok, so LCD is different from LCM... i get this now....
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