Series Completion Questions and Answers Reasoning

Directions to Solve

 

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

1.	120, 99, 80, 63, 48, ?
	A. 35 B. 38 C. 39 D. 40 EXPLANATION Answer: Option AExplanation:The pattern is – 21, – 19, – 17, – 15,…..So, missing term = 48 – 13 = 35.

2.	589654237, 89654237, 8965423, 965423, ?
	A. 58965 B. 65423 C. 89654 D. 96542 EXPLANATION Answer: Option DExplanation:The digits are removed one by one from the beginning and the end in order alternatelyso as to obtain the subsequent terms of the series.

3.	3, 10, 101,?
	A. 10101 B. 10201 C. 10202 D. 11012 EXPLANATION Answer: Option CExplanation:Each term in the series is obtained by adding 1 to the square of the preceding term.So, missing term = (101)2 + 1 = 10202.

4.	In the series 2, 6, 18, 54, …… what will be the 8th term ?
	A. 4370 B. 4374 C. 7443 D. 7434 EXPLANATION Answer: Option BExplanation: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.

5.	125,80,45,20,?
	A. 5 B. 8 C. 10 D. 12 EXPLANATION Answer: Option AExplanation:The pattern is – 45, – 35, – 25, …..So, missing term = 20 – 15 = 5.

					6.	1, 1, 4, 8, 9, 27, 16, ?
						A. 32 B. 64 C. 81 D. 256 EXPLANATION Answer: Option BExplanation: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.

		7.	1, 2, 3, 6, 9, 18, ?, 54
			A. 18 B. 27 C. 36 D. 81 EXPLANATION Answer: Option BExplanation:The pattern is x 2, x 3/2, x 2, x 3/2, x 2,…..So, missing term = 18 x 3/2 = 27.

8.	6, 13, 25, 51, 101, ?
	A. 201 B. 202 C. 203 D. 205 EXPLANATION Answer: Option CExplanation:The pattern is x 2 + 1, x 2 – 1, x 2 + 1, x 2 – 1,…..So, missing term = 101 x 2 + 1 = 203.

9.	5,6,9, 15, ?, 40
	A. 21 B. 25 C. 27 D. 33 EXPLANATION Answer: Option BExplanation:The pattern is + 1, + 3, + 6,….., i.e. + 1, + (1, + 2), + (1 + 2 + 3),…..So, missing term = 15 + (1 + 2 + 3 + 4) = 25.

---

10.	1, 3, 4, 8, 15, 27, ?
	A. 37 B. 44 C. 50 D. 55 EXPLANATION Answer: Option CExplanation:The sum of any three consecutive terms of the series gives the next term.So, missing number = 8 + 15 + 27 = 50.

11.	3, 4, 7, 7, 13, 13, 21, 22, 31, 34, ?
	A. 42 B. 43 C. 51 D. 52 EXPLANATION Answer: Option BExplanation:The given sequence is a combination of two series :I. 3, 7, 13, 21, 31, ? and II. 4, 7, 13, 22, 34The pattern in I is + 4, + 6, + 8, + 10,…..The pattern in II is + 3, + 6, + 9, + 12,….. So, missing term = 31 + 12 = 43.

12.	198, 194, 185, 169, ?
	A. 92 B. 112 C. 136 D. 144 EXPLANATION Answer: Option DExplanation:The pattern is – 4, – 9, – 16,…..i.e. – 22, – 32, – 42,…..So, missing pattern = 169 – 52 = 169 – 25 = 144.

---

13.	2, 3, 5,7,11,?, 17
	A. 12 B. 13 C. 14 D. 15 EXPLANATION Answer: Option BExplanation:Clearly, the given series consists of prime numbers starting from 2. So, the missingterm is the prime number after 11, which is 13.

---

14.	6, 12, 21, ?, 48
	A. 33 B. 38 C. 40 D. 45 EXPLANATION Answer: Option AExplanation:The pattern is + 6, + 9, + 12, + 15, …..So, missing term = 21 + 12 = 33.

---

15.	Which term of the series 5, 10, 20, 40, ….. is 1280?
	A. 10th B. 9th C. 8th D. None of these EXPLANATION Answer: Option BExplanation:Clearly, 5 x 2 = 10, 10 x 2 = 20, 20 x 2 = 40,…..So, the series is a G.P. in which a = 5 and r = 2.Let 1280 be the rath term of the series.Then, 5×2n-1 = 1280 & 2n-1 = 256 = 28 & n – 1 = 8 & n = 9.

16.	2, 5, 9, ?, 20, 27
	A. 14 B. 16 C. 18 D. 24 EXPLANATION Answer: Option AExplanation:The pattern is + 3, + 4, + 5, + 6,…..So, missing term = 9 + 5 = 14.

---

17.	2, 3, 3, 5, 10, 13, ?, 43, 172, 177
	A. 23 B. 38 C. 39 D. 40 EXPLANATION Answer: Option CExplanation:The pattern is + 1, x 1, + 2, x 2, + 3, x 3, + 4, x 4, + 5.So, missing term = 13 x 3 = 39.

---

18.	9, 27, 31, 155, 161, 1127, ?
	A. 316 B. 1135 C. 1288 D. 2254 EXPLANATION Answer: Option BExplanation:The pattern is x 3, + 4, x 5, + 6, x 7,…..So, missing term = 1127 + 8 = 1135.

---

19.	2, 1, 2, 4, 4, 5, 6, 7, 8, 8, 10, 11, ?
	A. 9 B. 10 C. 11 D. 12 EXPLANATION Answer: Option BExplanation:The given sequence is a combination of three series :I. 1st, 4th, 7th, 10th, 13th terms i.e. 2, 4, 6, 8, ?II. 2nd, 5th, 8th, 11th terms i.e. 1, 4, 7, 10III. 3rd, 6th, 9th, 12th terms i.e. 2, 5, 8, 11 Clearly, I consists of consecutive even numbers. So, the missing term is 10.

---

20.	Which of the following will not be a number of the series 1, 8, 27, 64, 125,…..?
	A. 256 B. 512 C. 729 D. 1000 EXPLANATION Answer: Option AExplanation:The given series consists of cubes of natural numbers only. 256 is not the cube ofany natural number.