A = (GCD) * _
B = (GCD) * _
C = (GCD) * _
LCM = 4 * GCD
A = (GCD)
B = (GCD) * (2)
C = (GCD) * (2)^2
Or
A = (GCD)
B = (GCD)
C = (GCD) * (2)^2
Or
A = (GCD)
B = (GCD) * (2)^2
C = (GCD) * (2)^2
I. At least one of the numbers is odd.
--> No
II. Two of the three numbers must be same.
--> "must" - NO
III. At least one number is the same as Greatest Common Factor.
--> YES
So, (III)
Is it the answer?
LCM GCF
This topic has expert replies
Source: Beat The GMAT — Data Sufficiency |
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theCodeToGMAT
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Hi kop,
In Roman Numeral questions, it's important to have the answer choices as reference. The way the answers are written will likely allow you to "skip" some of the math (and not have to deal with all 3 Roman Numerals). It's also worth noting that it's easier to prove what's NOT TRUE in these types of situations.
I. At least 1 is odd.
If we use 2, 2, and 8 then the LCM is 4 times the GCF.
Roman Numeral 1 is NOT TRUE
II. Two of the three numbers must be the same.
If we use 1, 2 and 4, then the LCM is 4 times the GCF
Roman Numeral 2 is NOT TRUE
III. At least one of the numbers = the GCF
I can't seem to find a way to eliminate this one, so I assume that it's true.
GMAT assassins aren't born, they're made,
Rich
In Roman Numeral questions, it's important to have the answer choices as reference. The way the answers are written will likely allow you to "skip" some of the math (and not have to deal with all 3 Roman Numerals). It's also worth noting that it's easier to prove what's NOT TRUE in these types of situations.
I. At least 1 is odd.
If we use 2, 2, and 8 then the LCM is 4 times the GCF.
Roman Numeral 1 is NOT TRUE
II. Two of the three numbers must be the same.
If we use 1, 2 and 4, then the LCM is 4 times the GCF
Roman Numeral 2 is NOT TRUE
III. At least one of the numbers = the GCF
I can't seem to find a way to eliminate this one, so I assume that it's true.
GMAT assassins aren't born, they're made,
Rich
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Mathsbuddy
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This is what I reckon:
3 values A, B, C must be composed of factors a, b, c and F:
A = 2 * a * F
B = 2 * b * F
C = 1 * c * F
where F = highest common factor
LCM = 4F, therefore a = b = c = 1
So,
A = 2 * F
B = 2 * F
C = 1 * F
I. At least one of the numbers is odd - Not necessarily as F can be odd or even.
II. Two of the three numbers must be same - True (A and B)
III. At least one number is the same as Greatest Common Factor - True (C)
3 values A, B, C must be composed of factors a, b, c and F:
A = 2 * a * F
B = 2 * b * F
C = 1 * c * F
where F = highest common factor
LCM = 4F, therefore a = b = c = 1
So,
A = 2 * F
B = 2 * F
C = 1 * F
I. At least one of the numbers is odd - Not necessarily as F can be odd or even.
II. Two of the three numbers must be same - True (A and B)
III. At least one number is the same as Greatest Common Factor - True (C)
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Mathsbuddy
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Hi Mathsbuddy,
In Quant questions that ask for "what MUST be true", you have to be thorough enough to prove what "COULD be true" vs. what "MUST be true." That difference will be the difference between getting the question right and getting it wrong.
GMAT assassins aren't born, they're made,
Rich
In Quant questions that ask for "what MUST be true", you have to be thorough enough to prove what "COULD be true" vs. what "MUST be true." That difference will be the difference between getting the question right and getting it wrong.
GMAT assassins aren't born, they're made,
Rich
