Number Series - Verbal and Reasoning

Directions to SolveIn each series, look for the degree and direction of change between the numbers. In other words, do the numbers increase or decrease, and by how much
Q1:

Look at this series: 8, 6, 9, 23, 87 , ... What number should come next?

A 128

B 226

C 324

D 429

ANS:D - 429

8 x 1 - 2 = 6
6 x 2 - 3 = 9
9 x 3 - 4 = 23
23 x 4 - 5 = 87
87 x 5 - 6 = 429 ...