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Question 12 - Figure it out - Page 114, 115 - Chapter 5 Class 6 - Prime Time (Ganita Prakash)
Last updated at August 14, 2026 by Teachoo
Class 6 (Ganita Prakash & Old NCERT)
Chapter 5 Class 6 - Prime Time (Ganita Prakash)
- Factors and Multiples
- Common Multiples
- Common Factors
- Idli Vada Game
- Jumpy Jackpot
- Figure it out - Page 110, 111
- Prime Numbers
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Figure it out - Page 114, 115
- Co-prime numbers (and art)
- Prime Factorisation
- Uses of Prime Factorisation
- Divisibility Tests
- Figure it out - Page 125, 126
- Fun with numbers
- Teachoo Questions - MCQs
- Teachoo Questions - Mix
- Teachoo Questions - Assertion Reasoning
- Teachoo Questions - Case Based
Transcript
Question 12 Observe that 3 is a prime number, and 2 × 3 + 1 = 7 is also a prime. Are there other primes for which doubling and adding 1 gives another prime? Find at least five such examples. Yes, here are five examples: For prime number 2: 2 × 2 + 1 = 5 And, 5 is a prime number For prime number 5: 2 × 5 + 1 = 11 And, 11 is a prime number For prime number 11: 2 × 11 + 1 = 23 And, 23 is a prime number For prime number 23: 2 × 23 + 1 = 47 And, 47 is a prime number For prime number 29: 2 × 29 + 1 = 59 And, 59 is a prime number
