N and R are integers. If N is divisible by 10^R, but cannot be divisible by 10^(R+1), R=?
1). N is divisible by 2^5, but cannot be divisible by 2^6.
2). N is divisible by 5^6, but cannot be divisible by 5^7.
[spoiler]OA not known, plz explain!!![/spoiler]
Divisibility
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- alivapriyada
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- shovan85
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Just giving a try ![Smile :)](./images/smilies/smile.png)
IMO C.
1. N=2^5(k) where k = 1,3,5,7,9,11,13,..... (Not multiple of 2 as 2^6 will not divide N)
Not Suff as u cannot say anything about R
2. N=5^6(k') where k' = 1,2,3,4,6,7,8,9,11,12,13,14...... (Not multiple of 5 as 5^7 will not divide N)
Not Suff as u cannot say anything about R
Now, combine both then N= (2^5) * (5^6) (k") where k" = 1,3,7,9,11,13,17.... (Not multiple of 2 and 5 as 10^(R+1) will not divide N)
N= (10^5) * 5 * k" and as we will not encounter any more 2 and 5 in k",R has to be 5.
Hope I am correct. Let me know if it helps or other suggestions are always welcome.
![Smile :)](./images/smilies/smile.png)
IMO C.
1. N=2^5(k) where k = 1,3,5,7,9,11,13,..... (Not multiple of 2 as 2^6 will not divide N)
Not Suff as u cannot say anything about R
2. N=5^6(k') where k' = 1,2,3,4,6,7,8,9,11,12,13,14...... (Not multiple of 5 as 5^7 will not divide N)
Not Suff as u cannot say anything about R
Now, combine both then N= (2^5) * (5^6) (k") where k" = 1,3,7,9,11,13,17.... (Not multiple of 2 and 5 as 10^(R+1) will not divide N)
N= (10^5) * 5 * k" and as we will not encounter any more 2 and 5 in k",R has to be 5.
Hope I am correct. Let me know if it helps or other suggestions are always welcome.
- alivapriyada
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shovan85 wrote:Just giving a try
IMO C.
1. N=2^5(k) where k = 1,3,5,7,9,11,13,..... (Not multiple of 2 as 2^6 will not divide N)
Not Suff as u cannot say anything about R
2. N=5^6(k') where k' = 1,2,3,4,6,7,8,9,11,12,13,14...... (Not multiple of 5 as 5^7 will not divide N)
Not Suff as u cannot say anything about R
Now, combine both then N= (2^5) * (5^6) (k") where k" = 1,3,7,9,11,13,17.... (Not multiple of 2 and 5 as 10^(R+1) will not divide N)
N= (10^5) * 5 * k" and as we will not encounter any more 2 and 5 in k",R has to be 5.
Hope I am correct. Let me know if it helps or other suggestions are always welcome.
many thanks for your explanation!!!!
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tobe honest, i dont take care of data these days, i only do PS and today when i take a look at this question, i guess it might be C but to tell me to solve it in detail i cant....and lucky me the answer is Calivapriyada wrote:N and R are integers. If N is divisible by 10^R, but cannot be divisible by 10^(R+1), R=?
1). N is divisible by 2^5, but cannot be divisible by 2^6.
2). N is divisible by 5^6, but cannot be divisible by 5^7.
[spoiler]OA not known, plz explain!!![/spoiler]
and i think i should review the way i study...