Proving 10^n Leaves Remainder 1 When Divided by 9

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In summary, to prove that 10^n leaves remainder 1 after dividing by 9, one can use modular arithmetic by showing that 10^n is equivalent to 1 mod 9. Another method is to use the binomial theorem and write (9+1)^n as a sum of terms, with the first term being 1 and the remaining terms all divisible by 9. Finally, one can also use induction by assuming that 10^n leaves a remainder of 1 and showing that 10^(n+1) also satisfies this condition.
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Dollydaggerxo
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Homework Statement


Prove that 10^n leaves remainder 1 after dividing by 9.

The Attempt at a Solution



There is an integer K, such that 10^n = 9k + 1

Where do i go from here if I want to do it just directly?
 
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Do you know modular arithmetic?
[tex]10^n \equiv 1^n =1 \pmod 9[/tex]
Alternatively use the binomial theorem by writing:
[tex](9+1)^n = \sum_{i=0}^n \binom{n}{i} 9^i = 1 + 9\sum_{i=1}^n \binom{n}{i}9^{i-1}[/tex]
Finally you could use induction by noting that if [itex]10^n = 9k+1[/itex], then,
[tex]10^{n+1} = 10^n 10 = (9k+1)(9+1) = 9^2k + 9k + 9 + 1[/tex]
I would call all approaches direct though induction may not qualify depending on your definition.
 

What is the concept of proving 10^n leaves remainder 1 when divided by 9?

The concept is based on the mathematical property that the remainder of dividing any power of 10 (10^n) by 9 is always 1. This can be proven through various mathematical methods such as induction, modular arithmetic, and divisibility rules.

Why is it important to prove this concept?

Proving this concept is important because it helps us understand the behavior of numbers when divided by 9. It also has practical applications in fields such as cryptography, computer science, and engineering.

Can this concept be extended to other numbers besides 10?

Yes, this concept can be extended to any number that is one less than a multiple of 9 (e.g. 11, 1001, 1000001). This is because all these numbers can be expressed as 9n+1, where n is any positive integer.

What are some real-life examples of this concept?

One example is the use of checksums in computer systems. In order to detect errors in transmitted data, a checksum is calculated by dividing the sum of all digits in a number by 9. If the remainder is 1, it is likely that the data has been transmitted correctly.

How can one prove this concept using induction?

Induction is a mathematical proof technique that involves proving a statement or property for all natural numbers. To prove that 10^n leaves remainder 1 when divided by 9, we can show that it is true for n=1, assume it is true for n=k, and then prove that it is also true for n=k+1. By doing this, we can show that the statement holds for all natural numbers, including 10^n.

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