Schooling · Class 7 · Mathematics · Large Numbers Around Us · Chapter on a page
CBSE Class 7 · Mathematics · NCERT Ganita Prakash
Large Numbers Around Us: chapter on a page
A cut of Shishya's notes for this chapter: the first paragraph of the introduction and the key ideas, formulas and facts, common mistakes and quick revision lists, word for word. Nothing is added or reworded; the worked examples are left out (they are on the chapter page).
About the notes: Written by Shishya's AI on 26 Sept 2026 from the chapter's title and class level, in Shishya's own words — not a copy or summary of the textbook. Read the official chapter for the book's own text, activities and exercises.
Fact-checked on 21 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain.
Mind map
Drawn from the same notes by a fixed rule (no AI): each label is the item's own words — its bold term, its label before a colon, a short formula as written, or its first words.
The mind map as a list
- Key ideas
- The Indian place value system groups…
- 1 lakh = 1,00,000 (one followed by…
- To compare two large numbers, first…
- Estimation means finding a value…
- When rounding, look at the digit…
- Large numbers can be written in…
- Formulas and facts
- 10 ones = 1 ten
- 100 thousands = 1 lakh
- 100 lakhs = 1 crore
- Place values from right
- Rounding rule
- Watch out for
- Writing commas in the wrong places…
- Confusing lakh and million
- Rounding 2,45,000 to the nearest…
- Forgetting zeros in the middle when…
- Reading digits one by one instead of…
What this chapter is about
This chapter helps you understand and work with very large numbers that appear in everyday life. Think about the population of India (more than one hundred crore people), the distance from Earth to the Moon (about 3,84,000 kilometres), or the money collected in a big cricket tournament. These numbers are so large that reading, writing and comparing them needs special care.
Key ideas
- The Indian place value system groups digits in sets: ones, tens, hundreds, then thousands (2 digits), then lakhs (2 digits), then crores (2 digits). Commas are placed after every two digits starting from the right, except the first group of three.
- 1 lakh = 1,00,000 (one followed by five zeros). 1 crore = 1,00,00,000 (one followed by seven zeros).
- To compare two large numbers, first count how many digits each has. The number with more digits is larger. If both have the same number of digits, compare from the leftmost digit.
- Estimation means finding a value close to the exact number. We round off to the nearest ten, hundred, thousand or lakh depending on how rough an answer we need.
- When rounding, look at the digit just after your rounding place. If it is 5 or more, round up; if it is less than 5, round down.
- Large numbers can be written in expanded form to show the value of each digit. For example, 23,45,678 = 20,00,000 + 3,00,000 + 40,000 + 5,000 + 600 + 70 + 8.
Formulas and facts to remember
- 10 ones = 1 ten; 10 tens = 1 hundred; 10 hundreds = 1 thousand.
- 100 thousands = 1 lakh (written 1,00,000).
- 100 lakhs = 1 crore (written 1,00,00,000).
- Place values from right: ones, tens, hundreds, thousands, ten-thousands, lakhs, ten-lakhs, crores.
- Rounding rule: digit ≥ 5 at the cut-off place means round up; digit < 5 means round down.
Common mistakes
- Writing commas in the wrong places, such as 34,56,78 instead of 3,45,678 → always group two digits at a time after the first three from the right.
- Confusing lakh and million → remember 1 lakh = 1,00,000 and 10 lakhs = 1 million = 10,00,000.
- Rounding 2,45,000 to the nearest lakh as 3,00,000 → check the ten-thousands digit (4), which is less than 5, so round down to 2,00,000.
- Forgetting zeros in the middle when writing in figures, writing "four lakh five thousand" as 4,5,000 instead of 4,05,000 → keep placeholders for empty positions.
- Reading digits one by one instead of in groups → practise reading in groups separated by commas.
Quick revision
- 1 lakh = 1,00,000; 1 crore = 1,00,00,000.
- Place commas after every two digits from the right, except the first group of three.
- More digits means a larger number; same digits, compare from the left.
- Round up when the cut-off digit is 5 or more; round down when it is less than 5.
- Expanded form shows each digit multiplied by its place value.