Check whether can end with the digit for any natural number .
Answer
No. can never end with the digit .
The correct answer is No. can never end with the digit . — Since never divides , neither does , and so cannot end in for any natural number .
Step-by-step solution
- A number ends with the digit only if it is divisible by .
- Since , such a number must have both and in its prime factorisation.
- Now factorise . Since , we get .
- The only primes appearing here are and . There is no factor of .
- By the Fundamental Theorem of Arithmetic the prime factorisation of a number is unique, so a factor of cannot appear from anywhere else.
- Since never divides , neither does , and so cannot end in for any natural number .
Common mistake: Testing a few values such as , and and concluding from those. Checking examples is not a proof; the argument has to rule out every at once.
Concept tested: Fundamental Theorem of Arithmetic
Published · How this solution was prepared and checked
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