MathsCBSE Class 10 · Standard · Board exam 2026, set 30/3/1 · 2 marks · Very short answer

CBSE Class 10 Mathematics Standard 2026: question 22(b)

Set in the CBSE Class 10 board exam of 2026, paper 30/3/1, section B, question 22(b), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q22(b) · 2 marks · Very short answerArithmetic Progressions

Find the sum of the first 28 terms of an A.P. whose $n^{t h}$ term is given by $a_{n} = 3 n - 2$ .

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 30/3/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Put n = 1 and n = 28 in the formula for $a_{n}$ .

Hint 2

Then use $S_{n} = \frac{n}{2} (first + last)$ .

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

First term: $a_{1} = 3 (1) - 2 = 1$ .
½ mark
28th term: $a_{28} = 3 (28) - 2 = 82$ .
½ mark
$S_{28} = \frac{28}{2} (a_{1} + a_{28}) = 14 (1 + 82)$ .
½ mark
$S_{28} = 14 \times 83 = 1162$ .
½ mark

Answer: $S_{28} = 1162$

Where the marks are

Finds $a_{1} = 1$ (½ mark)
Finds $a_{28} = 82$ (½ mark)
Uses $S_{28} = \frac{28}{2} (1 + 82)$ (½ mark)
Gets 1162 (½ mark)

Revise the chapter

Chapter: Arithmetic Progressions (notes, formulas, where marks are lost and every past question)
Topic: Finding nth Term from the Sum of n Terms

Practise this chapterBoard-style questions from Arithmetic Progressions, one at a time, marked against the answer key and marking points.Back to the full paper2026 board paper, set 30/3/1 (Standard): every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.

CBSE Class 10 Mathematics Standard 2026: question 22(b)

Hints

Step-by-step solution

Revise the chapter

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