Knowing Our Numbers
Place value, large numbers, estimation, and Indian vs International number systems.
Chapter Overview
1 Lakh = 1,00,000 and 1 Crore = 1,00,00,000 = 10 Million in the International system.
Knowing Our Numbers introduces large numbers, estimation, and the Indian and International place value systems. You learn to read, write, compare, and round numbers used in real life — population figures, distances, and money.
Place Value Systems
- Indian system: Ones, Tens, Hundreds, Thousands, Ten Thousands, Lakhs, Ten Lakhs, Crores
- International system: Ones, Tens, Hundreds, Thousands, Ten Thousands, Hundred Thousands, Millions
- 1 Lakh = 100 Thousand = 1,00,000
- 1 Crore = 10 Million = 1,00,00,000
Comparing and Ordering
- Compare from the leftmost differing digit
- Use place value tables for large numbers
- Indian system groups in pairs after thousands (lakh, crore)
Estimation
Rounding makes calculation faster. Round to nearest tens, hundreds, or thousands depending on how precise the answer must be. In word problems, estimation checks whether your final answer is reasonable.
- Nearest tens: look at the ones digit (≥5 round up)
- Nearest hundreds: look at the tens digit
- Use estimation to verify exact calculations
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Example 1: Expanded Form
Write 8,75,240 in expanded form (Indian system).
- 18 is in lakhs place → 8,00,000
- 27 is in ten-thousands → 70,000
- 35 is in thousands → 5,000
- 42 is in hundreds → 200; 4 is in tens → 40
Answer
8,00,000 + 70,000 + 5,000 + 200 + 40
Example 2: Rounding
The population of a town is 8,75,240. Round it to the nearest thousand.
- 1Look at the hundreds digit: 2.
- 22 < 5, so round down — keep thousands digit 5.
- 3Replace hundreds, tens, ones with 0.
Answer
8,75,000
Key Points to Remember
- ✓ Master both Indian and International place value charts
- ✓ Expanded form breaks numbers into place values
- ✓ Estimation is useful for quick checks in exams
- ✓ Read large numbers in groups of two digits after thousands in Indian system
Exam Tips
- • Draw place value table for confusing questions
- • Show rounding steps clearly for 2-mark questions
- • Check if question asks Indian or International format
Practice MCQs — Knowing Our Numbers
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
1 Crore is equal to how many millions?