Decimal System ke Baare mein Aur

Class 7 Maths · Chapter 3: Point ke Aage Ek Jhalak · NCERT Ganita Prakash section 3.8

Seekho

Jab point khisak jaaye: decimal ya ikaai ki galti gambhir ho sakti hai. Ek shahar ke daftar ne paise euro ki jagah cents mein gin kar bhej diye, lagbhag 100 guna zyaada. Ek hawaai jahaaz mein fuel kilogram ki jagah pounds mein bhara gaya aur hawa mein kam pad gaya. Davaai ki 0.05 mg ko 0.5 mg padhna = 10 guna khuraak!

0.5 = 10 × 0.05

Decimal jaisa, par decimal nahi: "dopahar ke 4.5 ghante baad" = 4:30 p.m., kyunki 0.5 ghanta = 30 minute (4:50 nahi!). "2.5 ft" chauda darwaza = 2 ft 6 inch, kyunki 1 ft = 12 inch. Cricket mein "5.5 overs" = 5 overs aur 5 gendein, kyunki over mein 6 gend: yahan point decimal point hai hi nahi.

0.5 hour = 30 min · 0.5 ft = 6 in

Thoda itihaas: jinke har 10, 100, 1000 hain, aise bhinn Śhrīdharāchārya (8vi sadi) jaise Bhaarateeya ganitagyon ke kaam mein milte hain. Lagbhag 950 CE mein al-Uqlīdisī ne apni "Bhaarateeya Ganit ke Adhyaay" pustak mein decimal likhaavat samjhaayi. Point (·) 16vi sadi mein aam hua; kuch desh ab bhi comma use karte hain (1 000,5).

Bhinn ko decimal mein: 1/2 = 5/10 = 0.5, 3/2 = 1.5, 1/4 = 25/100 = 0.25, 3/4 = 0.75, 1/5 = 2/10 = 0.2, 4/5 = 0.8. Pehle hara 10, 100 ya 1000 banao, phir decimal likho.

1/4 = 25/100 = 0.25

Explore: asli decimal ya nahi?

1. Har ek sort karo: kya point decimal point hai?

Yaad rakho

• Point aur ikaai par dhyaan: 0.5 mg, 0.05 mg ka 10 guna hai.
• Har point decimal point nahi: 0.5 ghanta = 30 min, 5.5 overs = 5 overs aur 5 gend.

Quick check

Train "subah 10 baje ke 2.5 ghante baad" chalti hai. Kab?

1. 12:30 p.m.
2. 12:50 p.m.
3. 12:05 p.m.
4. 12:25 p.m.

Socho

Agar 1 lakh log har ek 45 paise travel insurance dete hain, to rupaye mein kitna?

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.