Class 10 Maths MCQs on Sum of First n Terms of Arithmetic Progressions
CBSE Class 10 Mathematics – Sum of First n Terms of AP MCQs
Chapter 5: Arithmetic Progressions
Topic: Sum of First n Terms (Sₙ)
Based on NCERT | As per Latest CBSE Board Examination Pattern
1. The formula for sum of first n terms of an AP is:
Correct Answer: A
Explanation: The sum of first n terms is Sₙ = n/2 [2a + (n − 1)d].
Explanation: The sum of first n terms is Sₙ = n/2 [2a + (n − 1)d].
2. Another formula for Sₙ is:
Correct Answer: A
Explanation: Sₙ = n/2 (first term + last term).
Explanation: Sₙ = n/2 (first term + last term).
3. Find S₁₀ of AP: 2, 5, 8, ...
Correct Answer: C
Explanation: a=2, d=3.
S₁₀ = 10/2[2(2)+9×3] = 5[4+27] = 5×31 = 155. Correction: Correct sum is 155 (option missing; update options accordingly if needed).
Explanation: a=2, d=3.
S₁₀ = 10/2[2(2)+9×3] = 5[4+27] = 5×31 = 155. Correction: Correct sum is 155 (option missing; update options accordingly if needed).
3. Find S₁₀ of AP: 2, 5, 8, ...
Correct Answer: B
Explanation: S₁₀ = 10/2[4+27] = 5×31 = 155.
Explanation: S₁₀ = 10/2[4+27] = 5×31 = 155.
4. Find sum of first 20 natural numbers.
Correct Answer: B
Explanation: S₂₀ = 20/2(1+20)=10×21=210.
Explanation: S₂₀ = 20/2(1+20)=10×21=210.
5. Find S₁₅ of AP: 3, 7, 11, ...
Correct Answer: B
Explanation: a=3,d=4.
S₁₅=15/2[6+56]=15/2×62=15×31=465.
Explanation: a=3,d=4.
S₁₅=15/2[6+56]=15/2×62=15×31=465.
6. If a=5, d=3, find S₁₂.
Correct Answer: A
Explanation: S₁₂=12/2[10+33]=6×43=258.
Explanation: S₁₂=12/2[10+33]=6×43=258.
7. Sum of first 50 even numbers is:
Correct Answer: B
Explanation: Sₙ=n/2(2+100)=50/2×102=25×102=2550 (Correct answer: C; adjust options accordingly).
Explanation: Sₙ=n/2(2+100)=50/2×102=25×102=2550 (Correct answer: C; adjust options accordingly).
7. Sum of first 50 even numbers is:
Correct Answer: C
Explanation: AP: 2,4,...100.
S₅₀=50/2(2+100)=25×102=2550.
Explanation: AP: 2,4,...100.
S₅₀=50/2(2+100)=25×102=2550.
8. Find sum of first 25 terms of AP: 1, 4, 7, ...
Correct Answer: C
Explanation: a=1,d=3.
S₂₅=25/2[2+72]=25/2×74=25×37=925 (Correct is A; adjust).
Explanation: a=1,d=3.
S₂₅=25/2[2+72]=25/2×74=25×37=925 (Correct is A; adjust).
8. Find sum of first 25 terms of AP: 1, 4, 7, ...
Correct Answer: A
Explanation: S₂₅=25/2(1+73)=25/2×74=25×37=925.
Explanation: S₂₅=25/2(1+73)=25/2×74=25×37=925.
9. If Sₙ = n² + 3n, find first term.
Correct Answer: C
Explanation: Put n=1 ⇒ S₁=1+3=4.
Explanation: Put n=1 ⇒ S₁=1+3=4.
10. If Sₙ = 3n² + 2n, common difference is:
Correct Answer: A
Explanation: aₙ=Sₙ−Sₙ₋₁ ⇒ difference=6.
Explanation: aₙ=Sₙ−Sₙ₋₁ ⇒ difference=6.
11. If S₁₀=100 and S₉=81, 10th term is:
Correct Answer: A
Explanation: a₁₀=S₁₀−S₉=100−81=19.
Explanation: a₁₀=S₁₀−S₉=100−81=19.
12. If first term 2 and Sₙ=72 for n=8, d is:
Correct Answer: B
Explanation: 72=8/2[4+7d]=4(4+7d)=72 ⇒ d=3.
Explanation: 72=8/2[4+7d]=4(4+7d)=72 ⇒ d=3.
13. If AP decreasing, d is:
Correct Answer: B
Explanation: Negative d gives decreasing AP.
Explanation: Negative d gives decreasing AP.
14. Sum of first 100 natural numbers is:
Correct Answer: B
Explanation: S₁₀₀=100/2(1+100)=5050.
Explanation: S₁₀₀=100/2(1+100)=5050.
15. If Sₙ=2n²+n, find 5th term.
Correct Answer: A
Explanation: a₅=S₅−S₄=55−34=21.
Explanation: a₅=S₅−S₄=55−34=21.
16. Which formula directly uses last term?
Correct Answer: A
Explanation: This formula uses first and last term.
Explanation: This formula uses first and last term.
17. If first term 10, d=5, find S₁₀.
Correct Answer: C
Explanation: S₁₀=10/2(20+45)=5×65=325.
Explanation: S₁₀=10/2(20+45)=5×65=325.
18. If S₁₅=240 and a=4,d=2, verify true?
Correct Answer: B
Explanation: S₁₅=15/2(8+28)=15/2×36=270 ≠240.
Explanation: S₁₅=15/2(8+28)=15/2×36=270 ≠240.
19. If Sₙ linear in n, sequence is:
Correct Answer: A
Explanation: Sum of AP forms quadratic; difference linear.
Explanation: Sum of AP forms quadratic; difference linear.
20. Sum formula helps to:
Correct Answer: A
Explanation: It gives total of many terms directly.
Explanation: It gives total of many terms directly.
