Letter-Numbers ka Vichaar

Class 7 Maths · Chapter 4: Letter-Numbers wale Expressions · NCERT Ganita Prakash section 4.1

Seekho

Meher apne bhai Kabir se 4 saal badi hai. Jab Kabir 8 ka, Meher 12 ki; jab Kabir 20 ka, Meher 24 ki. Niyam hamesha wahi: Meher ki umar = Kabir ki umar + 4. Shabd likhne ki jagah ek akshar use karte hain: agar k Kabir ki umar hai, to Meher ki umar k + 4.

m = k + 4 · k = m − 4

Numbers ki jagah aane wale k aur m jaise akshar letter-numbers kehlaate hain, aur k + 4 jaise expressions algebraic expressions. Use karne ke liye akshar ki jagah number rakho: agar k = 23, to Meher 23 + 4 = 27 ki. Ulta, Kabir ki umar m − 4: agar Meher 20 ki, to Kabir 16 ka.

k = 23 → k + 4 = 27

Pattern: har "L" mein 2 tiliyan, to n L mein 2 × n tiliyan. Nariyal ₹35 ka aur gud ₹60 kilo: c nariyal aur j kg gud ka daam c × 35 + j × 60. 7 nariyal aur 4 kg ke liye: 245 + 240 = ₹485. Aise likha niyam formula kehlaata hai.

c × 35 + j × 60 → 7 × 35 + 4 × 60 = 485

Parimiti ke formula: bhuja q wale varg ki parimiti 4 × q; bhuja a wale samabahu tribhuj ki 3 × a; regular hexagon ki 6 × a. Shabdon ko expression mein: "ek number se 5 zyaada" = n + 5; "ek number se 4 kam" = n − 4; "ek number ke 13 guna se 2 kam" = 13 × n − 2.

13 × n − 2

Explore: shabd se expression.

1. Har vaakyaansh ko uske expression se milaao.

Yaad rakho

• Letter-number ek number ke liye hota hai; k + 4 jaisa expression algebraic hai.
• Maan ke liye akshar ki jagah number rakho; aise likha aam niyam formula hai.

Quick check

Chakki chalne mein 10 second leti hai, phir har kg ke 8 second. y kg ka samay kaunsa expression?

1. 10 + 8 × y
2. (10 + 8) × y
3. 10 × 8 × y
4. 10 × y + 8

Socho

Calendar mein w ke neeche ki tareekh w + 7 hai. w ke baayein aur upar ki tareekhein kya hain?

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.