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If a, b, and c are positive integers, what is the greatest common divi

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If a, b, and c are positive integers, what is the greatest common divi  [#permalink]

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New post 21 Dec 2018, 06:01
1
5
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

63% (01:27) correct 37% (01:33) wrong based on 104 sessions

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Math Expert
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Re: If a, b, and c are positive integers, what is the greatest common divi  [#permalink]

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New post 24 Dec 2018, 01:56
1
1
If a, b, and c are positive integers, what is the greatest common divisor of a, b and c?

GCD means the largest number which has all three numbers a, b and c in its table.

(1) The greatest common divisor of a and b is 3
this means GCD of a, b and c can be only 3, but we don't know if 3 is a factor of c or not.
If yes, GCD is 3, otherwise it is 1.

Insufficient

(2) The greatest common divisor of b and c is 4
this means GCD of a, b and c can be only 4, but we don't know if 4 is a factor of a or not.
If yes, GCD is 4, otherwise it is 1.

Insufficient

Combined..
It can be only 1

C
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Re: If a, b, and c are positive integers, what is the greatest common divi  [#permalink]

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New post 23 Dec 2018, 04:19
I got E.

Since by St#2 : b = 4x , c = 4y , not enough

And by St#1 : a = 3z , b = 3x , not enough

Combining ,in (c)
a= 3z
b = 3*4*x
c = 4*y

We cannot get common factor from here, hence (e)
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If a, b, and c are positive integers, what is the greatest common divi  [#permalink]

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New post 23 Dec 2018, 08:11
1
aru010 wrote:
I got E.

Since by St#2 : b = 4x , c = 4y , not enough

And by St#1 : a = 3z , b = 3x , not enough

Combining ,in (c)
a= 3z
b = 3*4*x
c = 4*y

We cannot get common factor from here, hence (e)


aru010

What about the number 1?

Cheers!
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Re: If a, b, and c are positive integers, what is the greatest common divi  [#permalink]

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New post 24 Dec 2018, 01:16
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Re: If a, b, and c are positive integers, what is the greatest common divi   [#permalink] 24 Dec 2018, 01:16
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