Series Completion

Choose the correct alternative that will continue the same pattern and replace the question mark in the given series.

1, 3, 4, 8, 15, 27, ?

Answer: (c)

The sum of any three consecutive terms of the series gives the next term.

So, missing number = 8 + 15 + 27 = 50.

5,6,9, 15, ?, 40

Answer: (b)

The pattern is + 1, + 3, + 6,....., i.e. + 1, + (1, + 2), + (1 + 2 + 3),.....

So, missing term = 15 + (1 + 2 + 3 + 4) = 25.

6, 13, 25, 51, 101, ?

Answer: (c)

The pattern is x 2 + 1, x 2 - 1, x 2 + 1, x 2 - 1,.....

So, missing term = 101 x 2 + 1 = 203.

1, 2, 3, 6, 9, 18, ?, 54

Answer: (b)

The pattern is x 2, x 3/2, x 2, x 3/2, x 2,.....

So, missing term = 18 x 3/2 = 27.

1, 1, 4, 8, 9, 27, 16, ?

Answer: (b)

The series consists of squares and cubes of consecutive natural numbers i.e. 12, 13, 22, 23, 32, 33, 42, .....

So, missing term = 43 = 64.

125,80,45,20,?

Answer: (a)

The pattern is - 45, - 35, - 25, .....

So, missing term = 20 - 15 = 5.

In the series 2, 6, 18, 54, …… what will be the 8th term ?

Answer: (b)

Clearly, 2 x 3 = 6, 6 x 3 = 18, 18 x 3 = 54,.....

So, the series is a G.P. in which a = 2, r = 3.

Therefore 8th term = ar8-1 = ar7 = 2 x 37 = (2 x 2187) = 4374.

3, 10, 101,?

Answer: (c)

Each term in the series is obtained by adding 1 to the square of the preceding term.

So, missing term = (101)2 + 1 = 10202.

589654237, 89654237, 8965423, 965423, ?

Answer: (d)

The digits are removed one by one from the beginning and the end in order alternately

so as to obtain the subsequent terms of the series.

120, 99, 80, 63, 48, ?

Answer: (a)

The pattern is - 21, - 19, - 17, - 15,.....

So, missing term = 48 - 13 = 35.