# Series Completion Questions and Answers page 1

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

**Answer**: 35

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

**2) 589654237, 89654237, 8965423, 965423, ?**

**Answer**: 96542

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

**3) 3, 10, 101,?**

**Answer**: 10202

**Explanation**: 3^{2} + 1 = 10, 10^{2} + 1 = 101, 101^{2} + 1 = 10202

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

**Answer**: 4374

**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,?**

**Answer**: 5

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

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

**Answer**: 64

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

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

**Answer**: 27

**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, ?**

**Answer**: 203

**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**

**Answer**: 25

**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,** ?

**Answer**: 50

**Explanation**: The sum of three consecutive terms of the series gives the next term So -> 8 + 15 + 27 = 50

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