Question 12 - Figure it out - Page 114, 115 - Chapter 5 Class 6 - Prime Time (Ganita Prakash)

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