Notes Maths Class 7 Chapter 1 Ganita Prakash

Notes For All Chapters – Ganita Prakash Class 7th

Large Numbers Around Us

1. Understanding Big Numbers

• One Lakh = 1,00,000
• One Crore = 1,00,00,000

These are very large numbers used in real-life contexts like population, distances, etc.

2. Place Value Systems

Indian System:

• Commas are placed like this: 1,00,00,000 (Crore) → groups of 3-2-2 from the right.

International System (American):

• Commas are placed like this: 100,000,000 (Hundred Million) → groups of 3-3-3 from the right.

Indian vs International Numbering System

3. Reading and Writing Numbers

• 3,00,600 → Three lakh six hundred
• 15,75,000 → Fifteen lakh seventy-five thousand

4. Approximation and Estimation

Exact numbers are not always needed.

Rounding off is useful in real life:

Round Up: 732 people → Order 750 sweets

Round Down: ₹470 → Say around ₹450

5. Getting a Feel of Large Numbers

• Statue of Unity = 180 m
• Kunchikal Falls = 450 m

Helps us compare large values to familiar ones.

6. Interesting Facts with Numbers

Blue whale weighs over 15,00,000 kg

Distance from Earth to Sun ≈ 1,47,000,000 km

A lakh people standing in a line can stretch up to 38 km

7. Creative Calculations

Using special calculators:

• +1, +10, +100, +1000 buttons
• Different ways to form the same number (e.g., 5072)

8. Patterns in Multiplication

Multiplying by 5 = (×10) ÷ 2

Quick calculations using patterns:

• 116 × 5 = 580
• 824 × 25 = 20600

Observed Patterns:

• 1-digit × 1-digit = 1 or 2-digit
• 2-digit × 2-digit = 3 or 4-digit
• 3-digit × 3-digit = 5 or 6-digit

9. Population Comparison

• Use tables to compare city populations.
• E.g., Mumbai (2011) = 1,24,42,373, up from 1,19,78,450 in 2001

10. Thought Experiments

Can 1 lakh buses hold Mumbai’s population?

• 1 bus = 50 people → 1,00,000 buses = 50 lakh people
• Mumbai’s population is over 1.24 crore, so NO.

11. Toothpick Digits Fun

• Numbers can be made with sticks (matchsticks).
• 5108 needs 20 sticks.
• Try rearranging sticks to make bigger numbers!

12. Important Conversions

• 1 lakh = 100 thousand
• 1 crore = 100 lakhs
• 1 billion = 100 crores
• 1 arab = 1,00,00,00,000