Number Series Questions

The given number series 9, 19, 21, 43, 45, ... follows a pattern that

ALternately (x 2 + 1) and  (x 1 + 2)

9 

9 x 2 + 1 = 19

19 x 1 + 2 = 21

21 x 2 + 1 = 43

43 x 1 + 2 = 45

45 x 2 + 1 = 91

Hence, the next number in the given sequence is 91.

By trial and error method from the given options,

'1' satisfies the above given equation.

The first letter moves three steps forward. The second letter moves two steps forward. The third letter moves three steps forward.

This is an alternating series in alphabetical order. The middle letters follow the order ABCDE. The first and third letters are alphabetical beginning with J. The third letter is repeated as a first letter in each subsequent three-letter segment.

Because the letters are the same, concentrate on the number series, which is a simple 2, 3, 4, 5, 6 series, and follows each letter in order.

The letters move 2, 2, 3, 3, 4, 4, ... steps forward.

In this series, the third letter is repeated as the first letter of the next segment. The middle letter, A, remains static. The third letters are in alphabetical order, beginning with R.

The given number series is 200, 200, 100, 300, 75, ?

It follows a pattern that,

200

200 x 1 = 200

200 / 2 = 100

100 x 3 = 300

300 / 4 = 75

75 x 5 = 375

Hence, the next number in the given number sequence is 375.