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# Set B contains all factors and multiples of 20. If x is divisible by

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Math Expert
Joined: 02 Sep 2009
Posts: 58381
Set B contains all factors and multiples of 20. If x is divisible by  [#permalink]

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08 Jan 2017, 08:12
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Difficulty:

35% (medium)

Question Stats:

66% (01:09) correct 34% (01:42) wrong based on 79 sessions

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Set B contains all factors and multiples of 20. If x is divisible by 20, then x must also be divisible by how many members of set B?

A. 4
B. 5
C. 6
D. 10
E. 20

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Re: Set B contains all factors and multiples of 20. If x is divisible by  [#permalink]

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08 Jan 2017, 09:51
Bunuel wrote:
Set B contains all factors and multiples of 20. If x is divisible by 20, then x must also be divisible by how many members of set B?

A. 4
B. 5
C. 6
D. 10
E. 20

x is divisible by 20 means that x is definitely divisible by all factors of 20. But we can’t be sure about divisibility of x by other multiples of 20: 20*2, 20*3 …. Our B is infinite set {0; +∞}, but we are definite only with part of it’s elements, which represent factors of 20.

$$20 = 2^2*5$$

# of factors =$$3*2 = 6$$

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Re: Set B contains all factors and multiples of 20. If x is divisible by  [#permalink]

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08 Jan 2017, 09:51
Bunuel wrote:
Set B contains all factors and multiples of 20. If x is divisible by 20, then x must also be divisible by how many members of set B?

A. 4
B. 5
C. 6
D. 10
E. 20

Factors of 20 = 1, 2, 4, 5, 10, 20
Multiples of 20 = 20 , 40 , 60, 80.....................

So, B = { 1, 2, 4, 5, 10, 20 40 , 60, 80..................... }

x/20 = Remainder 0

Let the minimum value of x = 20

Thus , x must be divisible by 1, 2, 4, 5, 10, 20

So, x must also be divisible by 6 members of set B

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Re: Set B contains all factors and multiples of 20. If x is divisible by  [#permalink]

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08 Jan 2017, 15:42
Set B = ( 1,2,4,5,10,20,40... )
x can be divisible only by 20 and factors of 20.
6
C
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Re: Set B contains all factors and multiples of 20. If x is divisible by  [#permalink]

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23 Jan 2019, 22:36
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: Set B contains all factors and multiples of 20. If x is divisible by   [#permalink] 23 Jan 2019, 22:36
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