The formula for solving the problem is as follow: an = a1 + (n - 1)d Where: n = number of figure in the sequence = 4 d = difference between successive number =? a1 = -1 a4 = 59 Insert the given values into the formula, 59 = -1 + (4 - 1)d 59 = -1 + 3d 59 + 1 = 3d 60 = 3d d = 60/3 = 20 Therefore, d = 20. This implies that, there is a difference of 20 between successive numbers. The number sequence is as follow: -1, 19, 39, 59.
