This is a mark problem And 1 / 21 + 202 / 2121 + 50505 / 2121 + 13131313 / 2121 1/2+3/4+5/6+… /… +97/98+99/100

1 / 21 + 202 / 2121 + 50505 / 212121 + 13131313 / 212121 after seeing this question, at first glance, there are a lot of problems, and I can't start. Then, the denominator is a multiple of 21, and the original formula is 1 / 21 + 101 * 2 / 101 * 21 + 10101 * 5 / 10101 * 21 + 1010101 * 13 / 1010101 * 21 = 1 / 21 + 2 / 21 + 5 / 21

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