Find remainder when (2∗4∗6∗8⋯∗2016)−(1∗3∗5∗7⋯∗2015) is divided by 2017

In summary, the mathematical expression for this problem is (2*4*6*8*...*2016) - (1*3*5*7*...*2015). To find the remainder when divided by 2017, the modulus operator can be used. This problem can also be solved using the Chinese Remainder Theorem. The number 2017 is significant because it is a prime number. This problem can be generalized for any series of even and odd numbers using the formula (a1*a2*a3*...*an)-(b1*b2*b3*...*bm), where a1 to an are even numbers and b1 to bm are odd numbers.
  • #1
kaliprasad
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$ ( 2 * 4 * 6 * 8 \cdots * 2016) - ( 1 * 3 * 5 * 7 \cdots * 2015)$ is divided by 2017 what is the remainder
 
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  • #2
Fun little problem.
First p=2017 is a prime congruent to 1 mod 4; i.e (p-1)/2 is even. Let $x=2\times4\times\cdots \times p-1$ and $y=1\times3\times5\cdots\times p-2$. Now there are (p-1)/2 factors in x. Write x in reverse order: $x=p-1\times p-3\times p-5\cdots p-(p-2)$. So mod p we see that $x=(-1)^{(p-1)/2}1\times3\times5\cdots\times p-2=y$. So x - y is 0 mod p. Notice the result is true for any prime that is 1 mod 4.
 
  • #3
johng said:
Fun little problem.
First p=2017 is a prime congruent to 1 mod 4; i.e (p-1)/2 is even. Let $x=2\times4\times\cdots \times p-1$ and $y=1\times3\times5\cdots\times p-2$. Now there are (p-1)/2 factors in x. Write x in reverse order: $x=p-1\times p-3\times p-5\cdots p-(p-2)$. So mod p we see that $x=(-1)^{(p-1)/2}1\times3\times5\cdots\times p-2=y$. So x - y is 0 mod p. Notice the result is true for any prime that is 1 mod 4.

above is correct but p need not be prime. you have not used the fact. 2017 is incidentally prime but this fact is not used.
 

FAQ: Find remainder when (2∗4∗6∗8⋯∗2016)−(1∗3∗5∗7⋯∗2015) is divided by 2017

What is the mathematical expression for this problem?

The mathematical expression is (2*4*6*8*...*2016) - (1*3*5*7*...*2015).

How do you find the remainder when divided by 2017?

To find the remainder, we can use the modulus operator (%) which gives the remainder when one number is divided by another. In this case, we would divide the result of the expression by 2017 and use the remainder as the answer.

Can this problem be solved without calculating the entire product?

Yes, it can be solved using a shortcut method called the Chinese Remainder Theorem. This method involves breaking down the problem into smaller parts and finding the remainder for each part, then combining them to find the final remainder.

What is the significance of using the number 2017 in this problem?

The number 2017 is a prime number, which means it is only divisible by 1 and itself. This makes it a useful number in mathematics, especially in problems involving remainders.

Can this problem be generalized for any series of even and odd numbers?

Yes, this problem can be generalized for any series of even and odd numbers. The formula would be (a1*a2*a3*...*an)-(b1*b2*b3*...*bm), where a1 to an are even numbers and b1 to bm are odd numbers.

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