NDA & NA Sequences & Series (AP/GP) Questions with Answers & Explanations

20 Sequences & Series (AP/GP) questions from the Mathematics section of NDA & NA, each with the correct answer and a worked explanation. Try each question first, then tap Show answer to check. When you're ready, take the timed chapter-wise test to see your all-India rank.

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Question 1

What is the 21st term of the AP: 10, 12, 14, …?

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Answer: (D) 50 aₙ = a + (n − 1)d = 10 + 20 × 2 = 50.

Question 2

What is the sum of the first 7 terms of the GP: 1, 3, 9, …?

A2187
B1093
C1822
D1092

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Answer: (B) 1093 Sₙ = a(rⁿ − 1)/(r − 1) = 1093.

Question 3

What is the 13th term of the AP: 11, 15, 19, …?

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Answer: (C) 59 aₙ = a + (n − 1)d = 11 + 12 × 4 = 59.

Question 4

What is the sum of the first 6 terms of the GP: 5, 15, 45, …?

A1820
B3035
C3645
D1815

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Answer: (A) 1820 Sₙ = a(rⁿ − 1)/(r − 1) = 1820.

Question 5

What is the sum of the first 25 terms of the AP: 19, 26, 33, …?

A2556
B650
C2750
D2575

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Answer: (D) 2575 Sₙ = n/2 [2a + (n − 1)d] = 2575.

Question 6

What is the sum of the first 7 terms of the GP: 2, 4, 8, …?

A252
B382
C254
D256

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Answer: (C) 254 Sₙ = a(rⁿ − 1)/(r − 1) = 254.

Question 7

What is the 18th term of the AP: 1, 6, 11, …?

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Answer: (A) 86 aₙ = a + (n − 1)d = 1 + 17 × 5 = 86.

Question 8

What is the sum of the first 6 terms of the GP: 2, 6, 18, …?

A728
B1458
C726
D1214

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Answer: (A) 728 Sₙ = a(rⁿ − 1)/(r − 1) = 728.

Question 9

What is the 15th term of the AP: 18, 23, 28, …?

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Answer: (C) 88 aₙ = a + (n − 1)d = 18 + 14 × 5 = 88.

Question 10

What is the sum of the first 6 terms of the GP: 1, 2, 4, …?

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Answer: (C) 63 Sₙ = a(rⁿ − 1)/(r − 1) = 63.

Question 11

What is the sum of the first 24 terms of the AP: 16, 20, 24, …?

A1584
B1472
C480
D1488

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Answer: (D) 1488 Sₙ = n/2 [2a + (n − 1)d] = 1488.

Question 12

What is the sum of the first 5 terms of the GP: 2, 4, 8, …?

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Answer: (C) 62 Sₙ = a(rⁿ − 1)/(r − 1) = 62.

Question 13

What is the sum of the first 24 terms of the AP: 19, 22, 25, …?

A528
B1265
C1356
D1284

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Answer: (D) 1284 Sₙ = n/2 [2a + (n − 1)d] = 1284.

Question 14

What is the sum of the first 5 terms of the GP: 4, 8, 16, …?

A128
B124
C188
D120

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Answer: (B) 124 Sₙ = a(rⁿ − 1)/(r − 1) = 124.

Question 15

What is the 26th term of the AP: 6, 8, 10, …?

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Answer: (D) 56 aₙ = a + (n − 1)d = 6 + 25 × 2 = 56.

Question 16

What is the sum of the first 4 terms of the GP: 5, 15, 45, …?

A195
B200
C335
D405

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Answer: (B) 200 Sₙ = a(rⁿ − 1)/(r − 1) = 200.

Question 17

What is the 23rd term of the AP: 5, 13, 21, …?

A181
B197
C189
D173

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Answer: (A) 181 aₙ = a + (n − 1)d = 5 + 22 × 8 = 181.

Question 18

What is the sum of the first 6 terms of the GP: 4, 12, 36, …?

A1452
B2916
C2428
D1456

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Answer: (D) 1456 Sₙ = a(rⁿ − 1)/(r − 1) = 1456.

Question 19

What is the sum of the first 23 terms of the AP: 19, 21, 23, …?

A943
B924
C989
D483

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Answer: (A) 943 Sₙ = n/2 [2a + (n − 1)d] = 943.

Question 20

What is the 13th term of the AP: 14, 18, 22, …?

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Answer: (A) 62 aₙ = a + (n − 1)d = 14 + 12 × 4 = 62.

These are RankerClub practice questions written in the NDA & NA pattern. They are not official SSC/IBPS/RRB papers.

NDA & NA Sequences & Series (AP/GP) Questions with Answers & Explanations

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