Page 1 of 1
Rangpur Secondary 2011/6
Posted: Wed Feb 02, 2011 6:49 pm
by Moon
Problem 6:
When $N$ is divided by $7$, the quotient is twice the remainder. What is the number greater than $7$ that must divide $N$?
Re: Rangpur Secondary 2011/6
Posted: Wed Feb 02, 2011 7:51 pm
by Tahmid Hasan
is the wanted number a prime?
if it isn't there is no soln.
let's express $N=7.2a+a$
let's input the possible values of $a=1,2,3,4,5,6$
then the numbers are not divisible by any prime greater than 7
Re: Rangpur Secondary 2011/6
Posted: Thu Feb 03, 2011 4:46 am
by Mehfuj Zahir
N=15a then must be divided by 15
Re: Rangpur Secondary 2011/6
Posted: Thu Feb 03, 2011 11:36 am
by leonardo shawon
no..actually it is if $N=15x$ [$x=1,2] and divisible by 7 then quotient is twice the remainder.
Re: Rangpur Secondary 2011/6
Posted: Thu Feb 03, 2011 11:58 am
by Mehfuj Zahir
For any natural number it is true.U should read the question carefully.
Re: Rangpur Secondary 2011/6
Posted: Thu Feb 03, 2011 6:41 pm
by leonardo shawon
sorry. Mistake
Re: Rangpur Secondary 2011/6
Posted: Thu Feb 03, 2011 8:07 pm
by Moon
No problem. We are here so that we may discuss and learn from our mistakes.
Re: Rangpur Secondary 2011/6
Posted: Thu Feb 03, 2011 9:07 pm
by *Mahi*
Here,$N$ must be equal to $15x$ where $x\neq7y$.Then $15$ is the answer.