Sequence 1 + 1 / (1 * 2) + 1 / (2 * 3) + ··· + 1 / (99 + 100)= 1/(99*100)

Sequence 1 + 1 / (1 * 2) + 1 / (2 * 3) + ··· + 1 / (99 + 100)= 1/(99*100)

1/1*2=1/1-1/2
1/2*3=1/2-1/3
1/3*4=1/3-1/4
Add 1 / 2, 1 / 3, 1 / 4 In the end, only 1-1 / 100 = 99 / 100 is left