# Series Completion Questions and Answers page 1

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1) 120, 99, 80, 63, 48, ?

Explanation: – 21, – 19, – 17, – 15,….. So -> 48 – 13 = 35

2) 589654237, 89654237, 8965423, 965423, ?

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

3) 3, 10, 101,?

Explanation: 32 + 1 = 10, 102 + 1 = 101, 1012 + 1 = 10202

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

Explanation: 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

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

5) 125,80,45,20,?

Explanation: – 45, – 35, – 25, ….. So -> 20 – 15 = 5

6) 1, 1, 4, 8, 9, 27, 16, ?

Explanation: 12, 13, 22, 23, 32, 33, 42, ….. So -> 43 = 64

7) 1, 2, 3, 6, 9, 18, ?, 54

Explanation: x 2, x 3/2, x 2, x 3/2, x 2,….. So -> 18 x 3/2 = 27

8)   6, 13, 25, 51, 101, ?

Explanation: x 2 + 1, x 2 – 1, x 2 + 1, x 2 – 1,….. So -> 101 x 2 + 1 = 203

9) 5,6,9, 15, ?, 40

Explanation: + 1, + 3, + 6,….., i.e. + 1, + (1, + 2), + (1 + 2 + 3),….. So -> 15 + (1 + 2 + 3 + 4) = 25

10) 1, 3, 4, 8, 15, 27, ?