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Re: If x is a positive integer such that the units digit of x^3 [#permalink]
09 Dec 2017, 19:35

If x^3 has 3 as unit digit, it must be 7^3 since it equals 343. The 7 has the following pattern 7 ^1 7 7^2 9 7^3 3 7^4 1 7^5 7 and so one So 7^15 has a 3 as unit digits. Since I did it quickly, I am pretty sure that it is false. Any help ?