Arithmetic › Decimals and repeating decimals › Decimal periods

101st digit of a period-200 reciprocal

University · ●●●○○ 50 pts

Let pp be a prime number such that the period of the decimal expansion of 1p\frac{1}{p} is 200. That is, 1p=0.XXXX…\frac{1}{p}=0.XXXX\ldots for some block XX of 200 digits, but 1p≠0.YYYY…\frac{1}{p}\neq 0.YYYY\ldots for every block YY with fewer than 200 digits. Find the 101st digit, counting from the left, of XX.

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repeating decimalsmultiplicative orderdifference of squaresprime divisorsmodular arithmetic