MathsCBSE Class 10 · Standard · Sample paper, session 2025-26 · 2 marks · Very short answer

CBSE Class 10 Mathematics Standard sample paper 2025-26: question 21(A)

From the official CBSE sample question paper for 2025-26, section B, question 21(A), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q21(A) · 2 marks · Very short answerArithmetic Progressions

The A.P 8, 10, 12,……. has 60 terms. Find the sum of last 10 terms.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

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

Hint 1

The last 10 terms run from the 51st term to the 60th term.

Hint 2

Use $S = \frac{n}{2} (first + last)$ for those 10 terms.

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.

Here $a = 8$ , $d = 10 - 8 = 2$ and $n = 60$ .
½ mark
Last term: $t_{60} = a + 59 d = 8 + 59 (2) = 126$ .
½ mark
The last 10 terms are $t_{51}$ to $t_{60}$ , with $t_{51} = 8 + 50 (2) = 108$ . Their sum $= \frac{10}{2} (t_{51} + t_{60}) = 5 (108 + 126) = 1170$ .
1 mark

Answer: 1170

Where the marks are

Identifies a = 8, d = 2 (½ mark)
Finds $t_{60} = 126$ (½ mark)
Finds $t_{51} = 108$ and the sum of the last 10 terms = 1170 (1 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 paperSample paper 2025-26 (Standard): every question, by section.

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CBSE Class 10 Mathematics Standard sample paper 2025-26: question 21(A)

Hints

Step-by-step solution

Revise the chapter

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