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Three bells ring at intervals… (Class 10 Maths 2023, Q26b)

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MathsCBSE Class 10 · Standard · Board exam 2023, set 30/2/1 · 3 marks · Short answer

CBSE Class 10 Mathematics Standard 2023: question 26(b)

Set in the CBSE Class 10 board exam of 2023, paper 30/2/1, section C, question 26(b), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q26(b) · 3 marks · Short answerCompetency-basedReal Numbers

Three bells ring at intervals of , and minutes. If all the three bells rang at a.m., when will they ring together again ?

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 30/2/1.

Hints

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

Hint 1

The bells ring together again at a time that is a multiple of every interval.

Hint 2

Find the least common multiple of 6, 12 and 18, then add it to 6 a.m.

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. The bells ring together again after LCM(6, 12, 18) minutes.
    , ,
    LCM

    2 marks

  2. So all three bells ring together again 36 minutes after 6 a.m., i.e. at 6:36 a.m.

    1 mark

Answer: At 6:36 a.m.

Where the marks are

  • Finds LCM of 6, 12, 18 = 36 (2 marks)
  • Concludes they ring together at 6:36 a.m. (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Real Numbers, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 30/2/1 (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.