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Prime Numbers

Class 6 Maths · Chapter 5: Prime Time · NCERT Ganita Prakash section 5.2

Seekho

Rohan ke paas 12 square tiles hain. Wo kai rectangles bana sakta hai: 1 × 12, 2 × 6 aur 3 × 4. Par 7 tiles se sirf ek rectangle banta hai, ek seedhi line, 1 × 7.

Jis number ke theek do factors hon, 1 aur khud, wo prime number hai: 2, 3, 5, 7, 11, 13 … Jiske do se zyada factors hon wo composite hai: 4, 6, 8, 9, 10 … Number 1 ka sirf ek factor hai, isliye wo na prime hai na composite.

Chhalni se primes dhoondhna: numbers likho. 2 par gola lagao aur 2 ke baaki multiples kaat do. 3 par gola lagao aur uske multiples kaato. 5 aur 7 ke saath bhi aisa hi. Jo bache (1 chhodkar) wo 100 tak ke saare primes hain. Ye tareeka 2,000 saal se purana hai!

Sirf ek even number prime hai: 2. Baaki har even number 2 se bhaag hota hai, isliye uske kam se kam teen factors hote hain.

Explore: rectangles banao, phir primes dhoondo.

  1. 12 squares ka rectangle banao (seedhi line nahi).
  2. Ab 7 squares try karo. Kya seedhi line ke alawa kuch ban sakta hai?
  3. 1 se 30 tak har prime number par tap karo.

Yaad rakho

  • Prime: theek do factors (1 aur khud). Composite: do se zyada. 1 dono nahi.
  • 2 akela even prime hai. Chhalni multiples kaatkar primes dhoondhti hai.

Quick check

Inme se kaunsa number prime hai?

  1. 21
  2. 27
  3. 29
  4. 33
Answer

29. 29 sirf 1 aur 29 se bhaag hota hai. 21 = 3 × 7, 27 = 3 × 9 aur 33 = 3 × 11.

Socho

Kabir kehta hai: 'Har odd number prime hai.' Kya wo sahi hai?

Ek answer

Nahi. 9 = 3 × 3, 15 = 3 × 5 aur 21 = 3 × 7 odd hain par composite. (Aur 2 prime hai par even hai.)

Practice

Teen levels (easy, medium, hard) ke naye sawaalon se practice karo, kuch hands-on, hints aur hal ke saath. Topic poora karne ke liye pichhle 5 mein se 4 sahi karo.