1. The nth term of an Arithmetic Progression (A.P.) is given by:
A. a + (n - 1)d
B. a + nd
C. a rⁿ⁻¹
D. a + (n + 1)d
Show Answer
Answer: A. a + (n - 1)d
Explanation: Standard formula for the nth term (aₙ) of an A.P. with first term 'a' and common difference 'd'.
2. If a, b, c are in A.P., then:
A. 2b = a + c
B. b² = ac
C. b = a + c
D. a + b = c
Show Answer
Answer: A. 2b = a + c
Explanation: Common difference d = b - a = c - b ⇒ 2b = a + c.
3. The sum of first n natural numbers is equal to:
A. n(n + 1) / 2
B. n(n - 1) / 2
C. n²
D. (n + 1) / 2
Show Answer
Answer: A. n(n + 1) / 2
Explanation: Sum of A.P. 1, 2, 3... n is Sₙ = n/2 (1 + n) = n(n + 1) / 2.
4. The nth term of a Geometric Progression (G.P.) is given by:
A. a rⁿ⁻¹
B. a rⁿ
C. a + (n - 1)r
D. a rⁿ⁺¹
Show Answer
Answer: A. a rⁿ⁻¹
Explanation: Standard formula for nth term of a G.P. with first term 'a' and common ratio 'r'.
5. If a, b, c are in G.P., then:
A. b² = ac
B. 2b = a + c
C. b = ac
D. a² = bc
Show Answer
Answer: A. b² = ac
Explanation: Common ratio r = b/a = c/b ⇒ b² = ac.
6. What is the 10th term of the G.P. 5, 25, 125, ...?
A. 5¹⁰
B. 5⁹
C. 5¹¹
D. 10⁵
Show Answer
Answer: A. 5¹⁰
Explanation: Here a = 5, r = 5. a₁₀ = a r⁹ = 5 × 5⁹ = 5¹⁰.
7. Sum of first n terms of a G.P. when r ≠ 1 is:
A. a(rⁿ - 1) / (r - 1)
B. a(1 - r) / (1 - rⁿ)
C. a rⁿ / (r - 1)
D. n a rⁿ⁻¹
Show Answer
Answer: A. a(rⁿ - 1) / (r - 1)
Explanation: Standard sum formula Sₙ = a(rⁿ - 1) / (r - 1) for r > 1.
8. The Geometric Mean (G.M.) between two positive numbers a and b is:
A. √(ab)
B. (a + b) / 2
C. ab / 2
D. √(a + b)
Show Answer
Answer: A. √(ab)
Explanation: G.M. G = √(ab) such that a, G, b are in G.P.
9. The Arithmetic Mean (A.M.) between two numbers a and b is:
A. (a + b) / 2
B. √(ab)
C. 2ab / (a + b)
D. a + b
Show Answer
Answer: A. (a + b) / 2
Explanation: Single A.M. between two numbers a and b is (a + b) / 2.
10. Relation between Arithmetic Mean (A) and Geometric Mean (G) of two distinct positive numbers is:
A. A > G
B. A < G
C. A = G
D. A G = 1
Show Answer
Answer: A. A > G
Explanation: For any two non-equal positive real numbers, A.M. is always greater than G.M. (A > G).
11. Find the sum of an infinite G.P. 1, 1/2, 1/4, 1/8, ... :
A. 2
B. 1
C. 3/2
D. Infinity
Show Answer
Answer: A. 2
Explanation: Infinite G.P. sum S_∞ = a / (1 - r) = 1 / (1 - 1/2) = 1 / (1/2) = 2.
12. Formula for sum of an infinite G.P. when |r| < 1 is:
A. a / (1 - r)
B. a / (r - 1)
C. a (1 - r)
D. 1 / (1 - r)
Show Answer
Answer: A. a / (1 - r)
Explanation: Sum to infinity for convergent G.P. (|r| < 1) is S_∞ = a / (1 - r).
13. The 7th term of the sequence defined by a = (-1)ⁿ⁻¹ n³ is:
A. 343
B. -343
C. 243
D. -243
Show Answer
Answer: A. 343
Explanation: a₇ = (-1)⁶ × (7)³ = 1 × 343 = 343.
14. Which term of the G.P. 2, 8, 32, ... is 131072?
A. 9th term
B. 8th term
C. 10th term
D. 7th term
Show Answer
Answer: A. 9th term
Explanation: a = 2, r = 4. 2 × 4ⁿ⁻¹ = 131072 ⇒ 4ⁿ⁻¹ = 65536 = 4⁸ ⇒ n - 1 = 8 ⇒ n = 9.
15. If the 3rd term of a G.P. is 4, then the product of its first 5 terms is:
A. 4⁵
B. 4³
C. 4⁴
D. 1024
Show Answer
Answer: A. 4⁵
Explanation: Product = a · (ar) · (ar²) · (ar³) · (ar⁴) = a⁵ r¹⁰ = (ar²)⁵ = 4⁵ = 1024.
16. The Geometric Mean of 3 and 27 is:
Show Answer
Answer: A. 9
Explanation: G.M. = √(3 × 27) = √81 = 9.
17. Arithmetic Mean of two numbers is 10 and their Geometric Mean is 8. The numbers are:
A. 16 and 4
B. 12 and 8
C. 18 and 2
D. 20 and 5
Show Answer
Answer: A. 16 and 4
Explanation: a + b = 20 and ab = 64. Roots of x² - 20x + 64 = 0 are x = 16, 4.
18. The common ratio of the G.P. 5/2, 5/4, 5/8, ... is:
A. 1/2
B. 2
C. 5/2
D. 1/4
Show Answer
Answer: A. 1/2
Explanation: Common ratio r = (5/4) / (5/2) = 1/2.
19. If Sₙ = n² p and Sₘ = m² p for an A.P., then Sₚ is equal to:
Show Answer
Answer: A. p³
Explanation: Since Sₙ ∝ n², sequence is A.P. with a = p, d = 2p. Sₚ = (p/2)[2p + (p-1)2p] = p³.
20. The 4th term of a G.P. is 2/3 and the 7th term is 16/81. Find the first term:
A. 9/4
B. 4/9
C. 2/9
D. 3/2
Show Answer
Answer: A. 9/4
Explanation: a7 / a4 = r³ = (16/81) / (2/3) = 8/27 ⇒ r = 2/3. a4 = a r³ = a(8/27) = 2/3 ⇒ a = 9/4.
21. Find the sum of the series 3 + 33 + 333 + ... to n terms:
A. (1/3) [10(10ⁿ - 1)/9 - n]
B. (1/3) [10ⁿ - 1]
C. (3/9) [10ⁿ⁺¹ - 10 - n]
D. (1/9) [10ⁿ - 1 - n]
Show Answer
Answer: A. (1/3) [10(10ⁿ - 1)/9 - n]
Explanation: S = 3/9 (9 + 99 + 999 + ...) = 1/3 [(10-1) + (10²-1) + ...] = (1/3) [10(10ⁿ - 1)/9 - n].
22. What is the sum of odd integers from 1 to 2001?
A. 1002001
B. 1000000
C. 2002000
D. 1001000
Show Answer
Answer: A. 1002001
Explanation: Sequence: 1, 3, 5 ... 2001. n = 1001. S = n² = (1001)² = 1002001.
23. Sum of the infinite G.P. 6, 1.2, 0.24, ... is:
A. 7.5
B. 7.2
C. 8
D. 6.5
Show Answer
Answer: A. 7.5
Explanation: a = 6, r = 1.2 / 6 = 0.2. S_∞ = 6 / (1 - 0.2) = 6 / 0.8 = 7.5.
24. If x, 2y, 3z are in A.P. and x, y, z are in G.P., then common ratio r of G.P. is:
Show Answer
Answer: A. 1/3
Explanation: 4y = x + 3z. Since y = xr and z = xr², 4xr = x + 3xr² ⇒ 3r² - 4r + 1 = 0 ⇒ r = 1/3 (for non-constant).
25. Number of terms in sequence 2, 4, 8, 16, ... 1024 is:
Show Answer
Answer: A. 10
Explanation: 2ⁿ = 1024 = 2¹⁰ ⇒ n = 10.
26. Insert 2 geometric means between 3 and 81:
A. 9, 27
B. 6, 18
C. 12, 36
D. 9, 18
Show Answer
Answer: A. 9, 27
Explanation: 3, G₁, G₂, 81 are in G.P. 81 = 3 r³ ⇒ r³ = 27 ⇒ r = 3. Terms are 3×3 = 9 and 9×3 = 27.
27. If -2/7, x, -7/2 are in G.P., then x is equal to:
Show Answer
Answer: A. ±1
Explanation: x² = (-2/7) × (-7/2) = 1 ⇒ x = ±1.
28. Sum of first n terms of a G.P. with a = 1, r = 2 is:
A. 2ⁿ - 1
B. 2ⁿ⁺¹ - 1
C. 2ⁿ
D. 2ⁿ⁻¹
Show Answer
Answer: A. 2ⁿ - 1
Explanation: Sₙ = 1(2ⁿ - 1) / (2 - 1) = 2ⁿ - 1.
29. The value of 0.999... in fractional form using infinite G.P. is:
A. 1
B. 9/10
C. 99/100
D. 0.9
Show Answer
Answer: A. 1
Explanation: 0.999... = 9/10 + 9/100 + ... = (9/10) / (1 - 1/10) = (9/10) / (9/10) = 1.
30. If A and G be A.M. and G.M. of two positive numbers, the quadratic equation having these numbers as roots is:
A. x² - 2Ax + G² = 0
B. x² - Ax + G = 0
C. x² + 2Ax + G² = 0
D. x² - 2Ax - G² = 0
Show Answer
Answer: A. x² - 2Ax + G² = 0
Explanation: Sum of roots = a + b = 2A, Product of roots = ab = G². Equation: x² - (sum)x + product = x² - 2Ax + G² = 0.