Evaluate the sum of coprime positive integers , where (the recurring decimal composed of the digits of base repeating infinitely).
Details & Assumptions :
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The rational number < 1 that will expand to the sequence 0 , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 repeated infinitely many times when converted to decimal form is 1 1 1 1 1 1 1 1 1 1 1 3 7 1 7 4 2 1 → 1 3 7 1 7 4 2 1 + 1 1 1 1 1 1 1 1 1 1 = 1 1 2 4 8 2 8 5 3 2 .
Proof:
Let S = 0 . 0 1 2 3 4 5 6 7 8 9 . Then 1 0 1 0 ∗ S = 1 2 3 4 5 6 7 8 9 . 0 1 2 3 4 5 6 7 8 9 .
Hence by subtraction, ( 1 0 1 0 − 1 ) S = 1 2 3 4 5 6 7 8 9 → S = 9 9 9 9 9 9 9 9 9 9 1 2 3 4 5 6 7 8 9 = 3 3 3 3 3 3 3 3 3 3 4 1 1 5 2 2 6 3 = 1 1 1 1 1 1 1 1 1 1 1 3 7 1 7 4 2 1 .