Need help with this

[keplaxo]

Let Z be the smallest integer for which 7Z has 2016 digits.
What is the units digit of Z?

 

[Dr.Peterson]

Let Z be the smallest integer for which 7Z has 2016 digits.
What is the units digit of Z?

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What topics have you studied that might be of use? I suspect you aren't just taking intermediate algebra.

Try using those ideas, and show us what you can do.