1 / 10 * 11 + 1 / 11 * 12 + 1 / 12 * 13= There's another question that won't be 2 * 3 / 1 + 3 * 4 / 1 + 4 * 5 / 1.99 * 100 / 1

1 / 10 * 11 + 1 / 11 * 12 + 1 / 12 * 13= There's another question that won't be 2 * 3 / 1 + 3 * 4 / 1 + 4 * 5 / 1.99 * 100 / 1

10 * 11 / 1 + 11 * 12 / 1 + 12 * 13 / 1 = 1 / 10-1 / 11 + 1 / 11-1 / 12 + 1 / 12-1 / 13 = 1 / 10-1 / 13 = 3 / 1302 * 3 / 1 + 3 * 4 / 1 + 4 * 5 / 1.99 * 100 / 1 = 1 / 2-1 / 3 + 1 / 3-1 / 4 + 1 / 4-1 / 5 +. + 1 / 99-1 / 100 = 1 / 2-1 / 100 = 49 / 100