The order of 1, negative half, one third, negative quarter, one fifth... Is as follows What is the 11th number from left in line 1998?

The order of 1, negative half, one third, negative quarter, one fifth... Is as follows What is the 11th number from left in line 1998?

First of all, the sign of a number is determined by its denominator. The odd denominator is positive, and the even denominator is negative. Without considering the sign, the denominator of the last number in the nth row shows the rule: 1,3,6,10 ··· the denominator of the last number in the nth row = 1 + 2 + ·· + n = n (n + 1) / 2, so the denominator of the last number in the 1997 row is 1997 * 1998 / 2 =

(1, 1 / 2, 1 / 3), (1 / 3, 1 / 4, 1 / 5). According to the arrangement rule, there are 3 fractions in the first 100 arrays

Note that the denominator of the second number in each array is 2n, so it is easy to infer that the three numbers in the 100th array are (1 / 199, 1 / 200, 1 / 201)