Each even term of the series is obtained by multiplying the previous term by 2. 2nd term = (1st term) x 2 = 6 x 2 = 12 4th term = (3rd term) x 2 = 48 x 2 = 96. 6th term = (5th term) x 2 = 384 x 2 =768. 4th term should be 96 instead of 100.