Anjaan Dhoondho

Class 7 Maths · Chapter 15: Anjaan ko Dhoondhna · NCERT Ganita Prakash section P2 7.1

Seekho

Kabir ke taraazu ke ek palde par 3 ek jaise dibbe aur 2 kg, doosre par 14 kg, aur wo barabar hai. Dono palde se 2 kg hataao: 3 dibbe 12 kg ke barabar, to ek dibba 4 kg. Dibbe ke liye x: 3x + 2 = 14. Do expressions ke barabar hone ka kathan equation hai; jo maan use sach banaaye wo hal (solution).

3x + 2 = 14 → 3x = 12 → x = 4

Dono taraf dibbe: 5 dibbe + 3 kg, 2 dibbe + 15 kg ke barabar. Har palde se 2 dibbe hataao: 3 dibbe + 3 kg = 15 kg. 3 kg hataao: 3 dibbe = 12 kg, to dibba 4 kg. Jo bhi karo, dono taraf karo, taraazu barabar rahega.

5x + 3 = 2x + 15 → x = 4

Tiliyan: tribhujon ki kataar 3, 5, 7, 9 … tiliyan leti hai, to sthaan n ko 2n + 1. Kaunsa sthaan theek 99 tiliyan leta hai? 2n + 1 = 99 hal karo: 2n = 98, n = 49. Kya 200 tiliyan? 2n = 199 ka poorn hal nahi (2n + 1 hamesha odd), to nahi. Do expressions ke barabar hone ka kathan equation hai, jismein baayaan paksh (LHS) aur daayaan paksh (RHS).

2n + 1 = 99 → n = 49

Hal jaanchna: maan waapas rakho. 3x + 2 = 14 mein x = 4 se 3 × 4 + 2 = 14 ✓, par x = 5 se 17 ✗. Kai equations ka ek hi hal ho sakta hai: 2x = 8, x + 6 = 10 aur 3x − 2 = 10 sab x = 4 se hal hote hain.

Explore: dibba tolo.

1. 3 dibbe + 2 kg, 14 kg ke barabar. Ek dibbe ka vazan set karo.
2. 4 dibbe + 1 kg, 1 dibba + 25 kg ke barabar. Ek dibba set karo.

Yaad rakho

• Equation kehta hai do expressions barabar; hal use sach banaata hai.
• Taraazu jaisa: dono taraf ek jaisa karo.

Quick check

3n + 1 = 31 ka hal kaunsa n?

1. 10
2. 11
3. 30
4. 9

Socho

Ek eent apne aadhe se 1 kg zyaada bhaari hai. Kitni bhaari?

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.