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Arithmetic Progressions Exemplar — Class 10 Mathematics NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 10 Mathematics chapter "Arithmetic Progressions Exemplar" — 6 important questions with detailed answers for CBSE board exam preparation.

TL;DR: Free step-by-step NCERT solutions for Class 10 Mathematics chapter "Arithmetic Progressions Exemplar" — 6 important questions with detailed answers fo…

By Syllab.in · Updated Jun 17, 2026

Key Questions Covered:

  1. If first term a = 5 and common difference d = 3, find 10th term.
  2. Find sum of first 20 terms of AP: 2, 5, 8, 11, ...
  3. Which term of AP 3, 8, 13, 18, ... is 78?
  4. Insert 3 arithmetic means between 5 and 21.
  5. Find sum of all two-digit natural numbers divisible by 4.
  6. If sum of n terms of AP is 3n^2 + 5n, find the AP.

Solutions Summary:

Question Status
If first term a = 5 and common difference d = 3, find 10t… ✓ Solved
Find sum of first 20 terms of AP: 2, 5, 8, 11, ... ✓ Solved
Which term of AP 3, 8, 13, 18, ... is 78? ✓ Solved
Insert 3 arithmetic means between 5 and 21. ✓ Solved
Find sum of all two-digit natural numbers divisible by 4. ✓ Solved
If sum of n terms of AP is 3n^2 + 5n, find the AP. ✓ Solved

Showing 6 of 6 questions

Q1: If first term a = 5 and common difference d = 3, find 10th term.

an = a + (n-1)d. a10 = 5 + (10-1)(3) = 5 + 27 = 32.

Q2: Find sum of first 20 terms of AP: 2, 5, 8, 11, ...

a = 2, d = 3, n = 20. Sn = n/2 [2a + (n-1)d] = 20/2 [2(2) + 19(3)] = 10[4 + 57] = 10(61) = 610.

Q3: Which term of AP 3, 8, 13, 18, ... is 78?

a = 3, d = 5. an = 78. 3 + (n-1)(5) = 78. (n-1)(5) = 75, so n - 1 = 15, thus n = 16. The 16th term is 78.

Q4: Insert 3 arithmetic means between 5 and 21.

If 3 means are inserted, sequence is 5, A1, A2, A3, 21 (5 terms total). Common difference d = (21 - 5)/(5 - 1) = 16/4 = 4. So means are 9, 13, 17.

Q5: Find sum of all two-digit natural numbers divisible by 4.

Sequence: 12, 16, 20, ..., 96. a = 12, d = 4, l = 96. n = (96 - 12)/4 + 1 = 21 + 1 = 22. Sn = n/2 (a + l) = 22/2 (12 + 96) = 11(108) = 1188.

Q6: If sum of n terms of AP is 3n^2 + 5n, find the AP.

Sn = 3n^2 + 5n. First term a = S1 = 3 + 5 = 8. For n ≥ 2, an = Sn - Sn-1 = 3n^2 + 5n - 3(n-1)^2 - 5(n-1) = 3(2n - 1) + 5 = 6n + 2. So a2 = 14, d = 6. AP: 8, 14, 20, 26, ...

Showing 6 of 6 questions. Visit the full page for complete solutions.

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