Arithmetic Expressions Dobara

Class 7 Maths · Chapter 4: Letter-Numbers wale Expressions · NCERT Ganita Prakash section 4.2–4.3

Seekho

Chapter 2 se jaldi dohraav: expression ko terms ke jod mein likho, phir adla-badli aur grouping se aasaan banao. 83 + 28 − 13 + 32 = (83 − 13) + (28 + 32) = 70 + 60 = 130. Aur 68 − (18 + 13) = 68 − 18 − 13 = 37: bracket se pehle minus andar ke chinh badalta hai.

83 + 28 − 13 + 32 = 130

× chinh hataana: 4 ke multiples 4, 8, 12, 16 … Teesra term 4 × 3 aur nth term 4 × n. Ise aam taur par 4n likhte hain: pehle number, phir akshar, bina × ke. To 7k ka matlab 7 × k, aur k = 4 par 7k = 28.

4n = 4 × n · 7k = 28 when k = 4

Maan nikaalna: m = 2 par 5m + 3 ke liye pehle 5m = 5 × 2 = 10, phir + 3 = 13. Bracket ke saath: m = −6 par 3(m + 1) = 3 × (−5) = −15. Do aksharon ke saath: f = 3 aur g = 1 par 2f − 2g = 6 − 2 = 4.

m = 2: 5m + 3 = 13

Galti pakdo: "Agar d = 6, to 3d = 36" galat hai: 3d ka matlab 3 × 6 = 18, 3 aur 6 saath-saath likhna nahi. "Agar a = −4, to 10 − a = 6" bhi galat: 10 − (−4) = 14. Akshar ki jagah number rakhte samay use bracket mein rakho, khaaskar negative number.

Explore: m = 2 par maan.

1. m = 2 par har expression ko uske maan se milaao.

Yaad rakho

• 4n ka matlab 4 × n: pehle number likho aur × chhod do.
• Maan ke liye akshar ki jagah number (bracket mein) rakho, phir bracket–terms–jod.

Quick check

s = 7 par 3s − 2 ka maan?

1. 19
2. 15
3. 35
4. 21

Socho

Agar r = 8 to 2r + 1 = 29 kehna galat kyun 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.