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GRE Math Challenge #47-A 'Q-group' is defined
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19 Sep 2014, 03:56
19 Sep 2014, 03:56
Expert Reply
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Question Stats:
48% (01:00) correct
51% (01:13) wrong based on 39 sessions
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A 'Q-group' is defined as a pair (a,b) where a,b are +ve integers and
b = (90 - a) / 5
After refering to above data, how many different Q-groups of +ve integers are there?
A) 10
B) 15
C) 17
D) 18
E) Infinite.
b = (90 - a) / 5
After refering to above data, how many different Q-groups of +ve integers are there?
A) 10
B) 15
C) 17
D) 18
E) Infinite.
Re: GRE Math Challenge #47-A 'Q-group' is defined
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07 Jun 2019, 08:36
07 Jun 2019, 08:36
1
Can anyone pls explain the above math ?
Regards,
Regards,
Re: GRE Math Challenge #47-A 'Q-group' is defined
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07 Jun 2019, 08:41
07 Jun 2019, 08:41
1
Got it.
b has to be a different positive integer.
as b=(90-a)/5, so, b will be integers only in the cases where a will be the multiples of 5- i.e. from 5 to 85. So, total 17 values. Not a=90, because (90-90)/5 gives no positive integer value for b. So , Total 17 Q-group values .
b has to be a different positive integer.
as b=(90-a)/5, so, b will be integers only in the cases where a will be the multiples of 5- i.e. from 5 to 85. So, total 17 values. Not a=90, because (90-90)/5 gives no positive integer value for b. So , Total 17 Q-group values .
