GCF / LCM DS Problem

[mlaboda]

Thank you for helping me understand this problem!

If x and y are positive integers, what is the value of xy?

1. The greatest common factor of x and y is 10.
2. The least common multiple of x and y is 180.

Ans. B

[RoadtoIVY]

For any two positive integers x and y:

xy = (GCF of x and y) X (LCM of x and y)
In this case, it would be 10 X 180 = 1800
so C is the answer.

[heshamelaziry]

For any two positive integers x and y:

xy = (GCF of x and y) X (LCM of x and y)
In this case, it would be 10 X 180 = 1800
so C is the answer.

But mlaboda says OA is B

[RoadtoIVY]

That is incorrect. Please refer to this page:
https://www.manhattangmat.com/forums/if- ... -t282.html

[mlaboda]

C is the correct answer. My original post was wrong. Thanks for keeping me honest!

[heshamelaziry]

For any two positive integers x and y:

xy = (GCF of x and y) X (LCM of x and y)
In this case, it would be 10 X 180 = 1800
so C is the answer.

Where this rule come from? could you please explain this rule by a simple example of two integers?

[palvarez]

For any two positive integers x and y:

xy = (GCF of x and y) X (LCM of x and y)
In this case, it would be 10 X 180 = 1800
so C is the answer.

Where this rule come from? could you please explain this rule by a simple example of two integers?

it is a simple proof, but hard to type here. Check here

https://books.google.com/books?id=KJwvt2 ... ax&f=false