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How many Prime factors does 2180 have?

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How many Prime factors does 2180 have?  [#permalink]

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New post 27 Jan 2019, 21:02
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Question Stats:

63% (01:27) correct 37% (01:12) wrong based on 57 sessions

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How many prime numbers between 1 and 100 are factors of 2180?

A. One
B. Two
C. Three
D. Four
E. Five

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How many Prime factors does 2180 have?  [#permalink]

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New post 27 Jan 2019, 21:29
Gmatprep550 wrote:
How many prime numbers between 1 and 100 are factors of 2180?

A. One
B. Two
C. Three
D. Four
E. Five



2180 = 10*218=2*5*2*109..

It is all about knowing if 109 is prime now..
Check for divisibility till 11 as 11^2>109...
So check for 2,3,5,7,11...
2 and 5 are already factors, so check for others..

Not divisible by 3 as sum of digits is 1+0+9=10, not divisible by 3
Check for 7 but 105 is 7*15, so 109 is not divisible and also 11*10=110..

So only 2 and 5

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Re: How many Prime factors does 2180 have?  [#permalink]

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New post 27 Jan 2019, 21:30
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Re: How many Prime factors does 2180 have?  [#permalink]

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New post 27 Jan 2019, 22:12
Bunuel wrote:
Gmatprep550 wrote:
How many prime numbers between 1 and 100 are factors of 2180?

A. One
B. Two
C. Three
D. Four
E. Five


This is a copy of the following OG question: https://gmatclub.com/forum/how-many-pri ... 44445.html


Hi Bunel,

This is a same type of question with same condition but there is a difference that above question do have prime factor out side 100 and the question you have mention do not hence I added it for practice of others.
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Press +1 Kudos if my post helped you a little and help me to ulcock the tests ;) Wish you all success

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Please let me know if I'm wrong somewhere and help me to learn :-)
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Re: How many Prime factors does 2180 have?   [#permalink] 27 Jan 2019, 22:12
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