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Solve the following system of… (Class 10 Maths 2025, Q21)

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MathsCBSE Class 10 · Standard · Board exam 2025, set 30/4/1 · 2 marks · Very short answer

CBSE Class 10 Mathematics Standard 2025: question 21

Set in the CBSE Class 10 board exam of 2025, paper 30/4/1, section B, question 21, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q21 · 2 marks · Very short answerPair of Linear Equations in Two Variables

Solve the following system of equations algebraically : ;

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 30/4/1.

Hints

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

Hint 1

Try elimination: make the coefficient of the same in both equations.

Hint 2

The LCM of 30 and 40 is 120, so multiply the first equation by 4 and the second by 3, then subtract.

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.

  1. Multiply the first equation by 4 and the second by 3 so that the coefficients of are equal:
    ...(i)
    ...(ii)

    1 mark

  2. Subtract (ii) from (i):

    ½ mark

  3. Substitute in :

    ½ mark

Answer:

Where the marks are

  • Makes the coefficients of one variable equal, e.g. and (1 mark)
  • Gets (½ mark)
  • Gets (½ mark)

Revise the chapter

Practise this chapterBoard-style questions from Pair of Linear Equations in Two Variables, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 30/4/1 (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.