Equal wills

What is the largest possible integer value of N N such that 2013 , 1320 2013, 1320 and 3201 3201 leave the same remainder r r when divided by N N ?


The answer is 99.

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11 solutions

Lewis Tough
Oct 27, 2013

If x is the number, then both 3201-2013 and 2013-1320 must be multiples of x. Therefore, we are looking for the GCD of 1188 and 693. Our answer is 99 .

Genious Boss. We have only read number theory, but you have applied it.

Surendra Ratha - 7 years, 7 months ago

*3201-2013

Lewis Tough - 7 years, 7 months ago

Excellent.................

Nihhaar Chandra Routhu - 7 years, 7 months ago

can u explain again...

rishabh rai - 7 years, 7 months ago

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3201-2013=1188, 2013-1920=693. The GCD (greatest common divisor) of the two answers can be used to find the value of N, where r is constant.

Lewis Tough - 7 years, 7 months ago

why the difference 3201-1320 is not under consideration when evaluating gcd?

Rohit Kanrar - 7 years, 7 months ago

Why are their differences also the multiples of x x ? Can you explain in brief?

Akshat Jain - 7 years, 7 months ago

We let assume that M-r represents the 3 numbers ( 2013, 1320, 3201) where M is divisible by N and r is the remainder.

We subtract the larger number to the number next to it to eliminate the remainder and get a larger value of divisible by N

(M2-r) - (M1-r) = M2-M1 , (M3-r) - (M2-r) = M3-M2

so

3201 - 2013 = 1188 , 2013 - 1320 = 693

Then we get both their prime factors

so 1188 = (11)(3)(3)(3)(2)(2) , 693 = (11)(3)(3)(7)

From these we can say that they have both (11)(3)(3) which is equals to 99

then N = 99

Sabab Ahad
Oct 27, 2013

We can state the problem as:

2013\congr (mod N) ... (1)

3201\congr (mod N) ... (2)

1320\congr (mod N) ... (3)

Subtracting the three equations we get:

(2)-(1) ... 1188\cong0 (mod N)

(2)-(3) ... 1881\cong0 (mod N)

(1)-(3) ... 693\cong0 (mod N)

Now if we take the [GCD] of the three numbers we get 99 and that is the largest number that will give you a reminder of r when 2013, 1320 and 3201 are divided by it.

Juan Rodrígez
Oct 28, 2013

Let's generalize. We can find the largest integer value that leaves the same remainder between two numbers doing their difference.

So the problem goes about finding the gcd of the differences of the three numbers

g c d ( 3201 2013 , 3201 1320 , 2013 1320 ) = gcd(3201-2013,3201-1320,2013-1320)=

= g c d ( 1188 , 1881 , 693 ) = 99 = gcd(1188,1881,693) = \boxed{99}

It's good that you want to generalize the problem.

However, you have merely made a statement (and it isn't clear what "doing their difference" means, or how it relates to the gcd), and have not provided any justification of the statement.

Calvin Lin Staff - 7 years, 7 months ago

We know that "N" must divide 2013-r, 1320-r, and 3201-r

From this, we can deduce that it can also divide 2013-1320, 3201-1320, and 3201-2013 because it fits an even amount of times (without extraneous remainder) 2013-r and 3201-r

The prime factorizations of 2013-1320 (693), 3201-1320 (1881), and 3201-2013 (1188) are, respectively, ) 3^2 x 7 x 11, 11 x 19 x 3^2, and 2^2 x 3^2 x 11.

The term 11x3^2, 99, appears in all three of these numbers.

Therefore, our solution is 99.

David Kroell
Nov 3, 2013

2013 - 1320 = 693

3201 - 2013 = 1188

3201 - 1320 = 1881

N = Greatest common divisor of 693, 1188, and 1881 = 99.

2013 ≡ 33 mod 99

1320 ≡ 33 mod 99

3201 ≡ 33 mod 99

2013 = 3 x 11 x 61 1320 = 2 x 2 x 2 x 3 x 5 x 11 = 3 x 11 x 40 3201 = 3 x 11 x 97 they have same product = 3 x 11 = 33 when the reminder of each product divided by 3, the equation will get the same reminder = 1 So, N = 33 x 3 = 99

Athul Nambolan
Nov 1, 2013

We know 1320 = N k + r 1320 = Nk+r 2013 = N p + r 2013 = Np+r 3201 = N v + r , v , p , k 3201= Nv + r , v, p, k are +integers whoose gcd is one.

our required answer is the g c d ( 3201 2013 , 3201 1320 , 2013 1320 ) gcd (3201-2013, 3201-1320, 2013 - 1320 ) as it eliminates r.

2013 1320 = 693 2013-1320=693

3201 2013 = 1188 3201-2013=1188

To let the three numbers leave the same remainder,the largest possible value of N = gcd ( 693 , 1188 ) = 99 N=\gcd(693,1188)=99

Ans= 99 99

Omar Monteagudo
Aug 28, 2015

For a number N has the property to make that the divisions of 2013, 1320 and 3201 by N leave the smae remainder, then N must divide their differences; namely:

  1. N must divide 2013 - 1320 = 693 = 3² x 11 x 7.
  2. N must divide 3201 - 2013 = 1188 = 3³ x 11 x 2².
  3. N must divide 3201 - 1320 = 1881 = 3² x 11 x 19.

Therefore the greatest number N for which the remainders are going to be the same is 3² x 11 = 99.

2013 1320 = 693 2013 - 1320 = 693 3201 2013 = 1188 3201 - 2013 = 1188 3201 1320 = 1881 3201 - 1320 = 1881

N N = Greatest common divisor of 693 , 1188 693, 1188 , and 1881 = 99 1881 = \boxed{99} .

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