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Prime Time (common factors and multiples) · Class 6

3 questions · English, हिन्दी, मराठी · answer key with explanations ·

NCERT: Class 6 Ganita Prakash, Chapter 5: Prime Time. Our own questions in the chapter's style, drafted with AI help, every answer checked step by step; teacher review pending. Hindi and Marathi: translation - review pending.

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Prime Time (common factors and multiples) · English

Name: ____________________Date: ____________

Questions

  1. What is the highest common factor (HCF) of 24 and 36?

  2. Two bells ring every 6 and 8 minutes. They ring together now. After how many minutes do they ring together again?

  3. What is the lowest common multiple (LCM) of 4 and 10?

Answer key

  1. 12 — 24 = 12 × 2 and 36 = 12 × 3; no bigger number divides both. HCF = 12.
  2. 24 — Multiples of 6: 6, 12, 18, 24. Multiples of 8: 8, 16, 24. First common one: 24.
  3. 20 — Multiples of 10: 10, 20. 20 is also a multiple of 4. LCM = 20.

अभाज्य समय (सार्व गुणनखंड और गुणज) · हिन्दी

नाम: ____________________तारीख़: ____________

प्रश्न

  1. 24 और 36 का महत्तम समापवर्तक (HCF) क्या है?

  2. दो घंटियाँ हर 6 और हर 8 मिनट में बजती हैं। अभी साथ बजीं। कितने मिनट बाद फिर साथ बजेंगी?

  3. 4 और 10 का लघुत्तम समापवर्त्य (LCM) क्या है?

उत्तर

  1. 12 — 24 = 12 × 2 और 36 = 12 × 3; इससे बड़ी कोई संख्या दोनों को नहीं बाँटती। HCF = 12।
  2. 24 — 6 के गुणज: 6, 12, 18, 24। 8 के गुणज: 8, 16, 24। पहला साझा: 24।
  3. 20 — 10 के गुणज: 10, 20। 20, 4 का भी गुणज है। LCM = 20।

मूळ संख्यांची वेळ (सामाईक विभाजक आणि पट) · मराठी

नाव: ____________________दिनांक: ____________

प्रश्न

  1. 24 आणि 36 चा मसावि (HCF) किती?

  2. दोन घंटा दर 6 आणि दर 8 मिनिटांनी वाजतात. आत्ता एकत्र वाजल्या. किती मिनिटांनी पुन्हा एकत्र वाजतील?

  3. 4 आणि 10 चा लसावि (LCM) किती?

उत्तरे

  1. 12 — 24 = 12 × 2 आणि 36 = 12 × 3; यापेक्षा मोठी संख्या दोघांना भाग जात नाही. मसावि = 12.
  2. 24 — 6 चे पट: 6, 12, 18, 24. 8 चे पट: 8, 16, 24. पहिला सामाईक: 24.
  3. 20 — 10 चे पट: 10, 20. 20 हा 4 चाही पट आहे. लसावि = 20.

A worked example

Is 91 a prime number?

  1. Test the primes whose square is not more than 91 (2, 3, 5, 7): 91 is odd, its digit sum 10 is not a multiple of 3, and it does not end in 0 or 5.
  2. Try 7: 7 × 13 = 91, so 91 has factors other than 1 and itself.

Answer: No: 91 = 7 × 13. Check: 7 × 13 = 91.

The common mistake

Thinking every odd number is prime. 9, 15, 21 and 91 are odd but not prime; and 1 is not prime either, because it has only one factor.

In the NCERT book

Ganita Prakash, Class 6 (Reprint 2026-27), Chapter 5: Prime Time, pages 107 to 139. Open the chapter (PDF).

Practise this topic online: 3 questions, marked as you go, with a hint after a wrong answer.

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