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If the least common multiple of two prime numbers x and y is 10, where

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Re: If the least common multiple of two prime numbers x and y is 10, where [#permalink]
Bunuel wrote:
If the least common multiple of two prime numbers x and y is 10, where x > y, then the value of 2x + y is

A. 7
B. 9
C. 11
D. 12
E. 21

LCM (x,y) = 10 and both x an y are prime.
The only values of x and y can be 5 and 2 (x = 5 and y = 2)

2x + y = 2*5 + 2 = 12

Correct Option: D
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Re: If the least common multiple of two prime numbers x and y is 10, where [#permalink]
Excellent Question.
Here is what i did on this one ->
Since x,y are primes and x>y---->
LCM(x,y) => Product of x*y

Hence 10=xy
10=> 2*5

Thus x=5 ans y=2

So 2x+y=> 12

SMASH THAT D
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Re: If the least common multiple of two prime numbers x and y is 10, where [#permalink]
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Bunuel wrote:
If the least common multiple of two prime numbers x and y is 10, where x > y, then the value of 2x + y is

A. 7
B. 9
C. 11
D. 12
E. 21

2 and 5 are the only PRIME numbers with an LCM of 10
Since we're told x > y, we can conclude that x = 5 and y = 2

So, 2x + y = 2(5) + 2 = 12

Cheers,
Brent
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Re: If the least common multiple of two prime numbers x and y is 10, where [#permalink]
Top Contributor
Theory: If two numbers are co-prime (have no common factor apart from 1) then their LCM = product of those numbers

If the least common multiple of two prime numbers x and y is 10
Simce x and y are prime so they will have only one common factor between them which is 1
=> x and y are co-prime numbers
So, LCM(x,y) = x*y = 10
So, x and y can be 2 and 5
But we know that x > y
=> x= 5 and y =2

2x + y = 2*5 + 2 = 12

Hope it helps!

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Re: If the least common multiple of two prime numbers x and y is 10, where [#permalink]
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Re: If the least common multiple of two prime numbers x and y is 10, where [#permalink]
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