SEQUENCES AND SERIES-Objective Questions for Entrance Exams

Sequences and Series form a foundational pillar of higher secondary and competitive mathematics, linking algebraic structure with analytical reasoning. The following set of 50 objective-type questions has been carefully curated to reflect the conceptual depth, problem patterns, and mathematical rigor consistently observed in national-level entrance examinations such as JEE (Main and Advanced), NEET, AIIMS, BITSAT, KVPY, Olympiads, and major state engineering tests. Each question emphasizes clarity of formulation, economy of computation, and examination-oriented thinking, while remaining firmly grounded in standard NCERT theory. The coverage spans arithmetic, geometric, and harmonic progressions, special sums, telescoping series, convergence concepts, AM–GM relations, and classical identities frequently tested under time constraints. Detailed explanations accompany every answer to reinforce conceptual understanding and to highlight efficient solution strategies. Collectively, these MCQs are designed not merely for practice, but for sharpening mathematical intuition and exam readiness in a manner aligned with real competitive standards.

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Exercise

SEQUENCES AND SERIES

by Academia Aeternum

1. If the sum of the first \(n\) terms of an A.P. is \(3n^2+5n\), then its \(n\)th term is
(Exam: IIT-JEE Year: 1998)
2. The number of terms in the A.P. \(5,9,13,\dots,405\) is
(Exam: AIEEE Year: 2006)
3. If the A.M. and G.M. of two positive numbers are \(10\) and \(8\) respectively, the numbers are
(Exam: NEET Year: 2014)
4. The sum of an infinite G.P. with first term \(3\) and ratio \(\frac12\) is
(Exam: IIT-JEE Year: 1995)
5. If \(a,b,c\) are in G.P. and \(a+b+c=21\), then \(b\) equals
(Exam: KVPY Year: 2012)
6. The sum of first \(n\) odd natural numbers is
(Exam: Olympiad Year: 2001)
7. If the 5th term of an A.P. is 20 and 9th term is 36, the first term is
(Exam: IIT-JEE Year: 2003)
8. The value of \(1+\frac12+\frac14+\frac18+\cdots\) is
(Exam: BITSAT Year: 2010)
9. If \(a_n=\frac{1}{n(n+1)}\), then \(\sum_{k=1}^n a_k\) equals
(Exam: IIT-JEE Year: 2001)
10. If the common ratio of a G.P. is negative, then
(Exam: NEET Year: 2016)
11. The arithmetic mean between \(4\) and \(20\) is
(Exam: State Engg. Year: 2008)
12. The geometric mean between \(4\) and \(16\) is
(Exam: NEET Year: 2011)
13. If \(S_n=2^n-1\), then the sequence is
(Exam: IIT-JEE Year: 1997)
14. The sum of first \(n\) terms of A.P. with \(a=2,d=3\) is
(Exam: AIEEE Year: 2005)
15. If the sum of infinite G.P. is 4 and first term is 2, the common ratio is
(Exam: IIT-JEE Year: 1994)
16. The 10th term of the sequence \(n^2\) is
(Exam: Olympiad Year: 2004)
17. If \(a,b,c\) are in A.P. and \(b,c,d\) in G.P., then \(a,c,d\) are
(Exam: IIT-JEE Year: 2007)
18. The sum \(1^2+2^2+\cdots+n^2\) equals
(Exam: NEET Year: 2013)
19. If the middle term of an odd-term G.P. is \(m\), then the product of all terms is
(Exam: IIT-JEE Year: 1999)
20. The harmonic mean of \(a\) and \(b\) is
(Exam: State Engg. Year: 2009)
21. If the sum of the first \(n\) terms of a G.P. is \(S_n=3(2^n-1)\), then the first term is
(Exam: IIT-JEE Year: 1996)
22. The number of arithmetic means between 7 and 77 such that the sequence is an A.P. with common difference 7 is
(Exam: AIEEE Year: 2004)
23. If \(a_n=3n-5\), then the sequence is
(Exam: BITSAT Year: 2011)
24. The sum of the first 20 terms of the series \(2+4+6+\cdots\) is
(Exam: State Engg. Year: 2007)
25. If the ratio of the sum of first \(n\) terms of two A.P.s is independent of \(n\), then the ratio of their first terms equals the ratio of their
(Exam: IIT-JEE Year: 2002)
26. The value of \(1\cdot2+2\cdot3+3\cdot4+\cdots+n(n+1)\) is
(Exam: NEET Year: 2015)
27. If \(a,b,c\) are in H.P., then
(Exam: Olympiad Year: 2003)
28. The common ratio of the G.P. whose terms are squares of the terms of an A.P. is
(Exam: IIT-JEE Year: 1993)
29. If the sum of three numbers in G.P. is 21 and their product is 343, the middle term is
(Exam: NEET Year: 2010)
30. The sum of first \(n\) natural numbers is
(Exam: State Engg. Year: 2005)
31. If \(a_n=\frac{2n+1}{n+1}\), then \(\lim_{n\to\infty}a_n\) equals
(Exam: IIT-JEE Year: 2008)
32. The sum of cubes of first \(n\) natural numbers equals
(Exam: NEET Year: 2017)
33. If the first term of an A.P. is 1 and the sum of first \(n\) terms is \(n^2\), the common difference is
(Exam: IIT-JEE Year: 2000)
34. The sequence \(1,-\frac12,\frac14,-\frac18,\dots\) is
(Exam: BITSAT Year: 2013)
35. If the sum of infinite G.P. is finite, then
(Exam: IIT-JEE Year: 1992)
36. The arithmetic mean of roots of \(x^2-6x+8=0\) is
(Exam: NEET Year: 2012)
37. If \(a,b,c\) are in A.P., then \(2b\) equals
(Exam: Olympiad Year: 2002)
38. The sum of the series \(\frac12+\frac14+\frac18+\cdots+\frac1{2^n}\) is
(Exam: AIEEE Year: 2009)
39. If the \(n\)th term of an A.P. is \(7-3n\), then the common difference is
(Exam: State Engg. Year: 2010)
40. The geometric mean between 2 and 8 is
(Exam: NEET Year: 2009)
41. If the sum of first \(n\) terms of an A.P. is proportional to \(n^2\), then the first term is
(Exam: IIT-JEE Year: 1991)
42. The series \(1+\frac13+\frac15+\cdots\) is
(Exam: Olympiad Year: 2006)
43. If the sum of three consecutive terms of an A.P. is 21 and their product is 231, the middle term is
(Exam: NEET Year: 2018)
44. The sum of the first 100 natural numbers is
(Exam: State Engg. Year: 2006)
45. If \(a,b,c\) are positive and in G.P., then
(Exam: IIT-JEE Year: 1990)
46. The sum of the series \(1-1+1-1+\cdots\) is
(Exam: Olympiad Year: 2008)
47. If the common difference of an A.P. is zero, the sequence is
(Exam: NEET Year: 2019)
48. The value of \(\sum_{k=1}^n(2k-1)\) is
(Exam: AIEEE Year: 2007)
49. If the ratio of successive terms of a sequence tends to 1, then the sequence is necessarily
(Exam: IIT-JEE Year: 2009)
50. The sum of the first \(n\) terms of the sequence \(1,3,6,10,\dots\) is
(Exam: Olympiad Year: 2005)

Frequently Asked Questions

A sequence is an ordered list of numbers written according to a definite rule, where each number is called a term of the sequence.

In a sequence, order matters and repetition is allowed, whereas in a set order does not matter and repetition is not allowed.

The nth term is the general term of a sequence that represents the term at position \(n\).

A finite sequence has a limited number of terms, such as \(2,4,6,8\).

An infinite sequence has infinitely many terms, such as \(1,2,3,\dots\).

A series is the sum of the terms of a sequence.

A sequence lists terms, while a series represents their sum.

An arithmetic progression is a sequence in which the difference between consecutive terms is constant.

The common difference \(d\) is the difference between any term and its preceding term.

The general form of an AP is \(a, a+d, a+2d, a+3d, \dots\).

The nth term of an AP is given by \(a_n = a + (n-1)d\).

The symbol \(a\) represents the first term of the arithmetic progression.

The common difference is found by dividing the difference of the terms by the difference of their positions.

An arithmetic mean is a number inserted between two numbers such that all three form an AP.

The arithmetic mean is \(\dfrac{a+b}{2}\).

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