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GRE Prep Club Team Member
Joined: 20 Feb 2017
Posts: 2506
Given Kudos: 1055
GPA: 3.39
How many integers less than 1000 have no factors (other than 1) in com
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20 Sep 2021, 04:55
20 Sep 2021, 04:55
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Question Stats:
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25% (01:13) wrong based on 4 sessions
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How many integers less than 1000 have no factors (other than 1) in common with 1000?
A. 400
B. 401
C. 410
D. 420
E. 421
A. 400
B. 401
C. 410
D. 420
E. 421
Re: How many integers less than 1000 have no factors (other than 1) in com
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21 Sep 2021, 06:20
21 Sep 2021, 06:20
GeminiHeat wrote:
How many integers less than 1000 have no factors (other than 1) in common with 1000?
Number of integers less than 1000 = 1000 - 1 = 999,
Factors of 1000 are 2^3 * 5^3. So just check for prime factors 2 and 5.
Factors of 2 are 1/2 the numbers from 2 to 998 = 499
and Factors of 5, but not 2 are 5,15,...995 = 100
So 999 - 499 - 100 = 400.
Answer is A) 400
gmatclubot
Re: How many integers less than 1000 have no factors (other than 1) in com [#permalink]
21 Sep 2021, 06:20
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