NCERT Solutions for Class 7th Maths Chapter 1 Large Numbers Around Us
Updated on 2026-09-19
About this chapter
1 lakh = 1,00,000 (1 followed by 5 zeroes); 1 crore = 1,00,00,000 (7 zeroes); 1 arab = 1,00,00,00,000 (9 zeroes). Indian system groups digits 3-2-2-2 from the right (thousand, lakh, crore); the American/International system groups them 3-3-3 (thousand, million, billion). 1 million = 10 lakh, 1 billion = 100 crore = 1 arab, and 10,000 lakh make one billion. Big numbers become meaningful when you compare them with something familiar — Somu's 40 m building, a 100-year lifetime, the seats in a stadium. Rounding up, rounding down and the five 'nearest neighbours' (nearest thousand, ten thousand, lakh, ten lakh, crore) let you answer questions quickly without exact arithmetic. Regrouping factors makes multiplication easy: ×5 is ÷2 then ×10, ×25 is ×100 then ÷4, ×125 is ×1000 then ÷8. An m-digit
- .1 A Lakh Varieties!
- (Getting a Feel of Large Numbers)1.1 A Lakh Varieties!
- Reading and Writing Numbers
- .2 Land of Tens
- .3 Of Crores and Crores!
- .4 Exact and Approximate Values
- (Nearest Neighbours)1.4 Exact and Approximate Values
- .5 Patterns in Products
- (How Long is the Product?)1.5 Patterns in Products
- .6 Did You Ever Wonder…?
Quick revision
| Number | Indian system | In words (Indian) | American system |
|---|---|---|---|
| 103 | 1,000 | One thousand | 1,000 — one thousand |
| 104 | 10,000 | Ten thousand | 10,000 — ten thousand |
| 105 | 1,00,000 | One lakh | 100,000 — hundred thousand |
| 106 | 10,00,000 | Ten lakh | 1,000,000 — one million |
| 107 | 1,00,00,000 | One crore | 10,000,000 — ten million |
| 108 | 10,00,00,000 | Ten crore | 100,000,000 — hundred million |
| 109 | 1,00,00,00,000 | One arab (hundred crore) | 1,000,000,000 — one billion |
| Shortcut | × 5 | = ÷ 2, then × 10 | 116 × 5 = 58 × 10 = 580 |
| Shortcut | × 25 | = × 100, then ÷ 4 | 824 × 25 = 82400 ÷ 4 = 20,600 |
| Shortcut | × 125 | = × 1000, then ÷ 8 | 72 × 125 = 72000 ÷ 8 = 9,000 |
| Digits rule | m-digit × n-digit | (m + n − 1) or (m + n) digits | 3-digit × 3-digit = 5 or 6 digits |
| Least clicks | +1, +10, +100 … buttons | Smallest number of clicks = digit sum | 5072 → 5 + 0 + 7 + 2 = 14 clicks |
Exercises
- .1 A Lakh Varieties! — In-text Questions Page 1–21
- .1 A Lakh Varieties! — In-text Questions Page 31
- .1 A Lakh Varieties! — Figure it Out Page 31
- (Getting a Feel of Large Numbers)1.1 A Lakh Varieties! — In-text Questions Page 3
- Reading and Writing Numbers — In-text Questions Page 4–5
- .2 Land of Tens — Land of Tens Page 5–61
- .2 Land of Tens — Figure it Out Page 61
- .2 Land of Tens — In-text Questions Page 71
- .2 Land of Tens — Figure it Out Page 71
- .3 Of Crores and Crores! — In-text Questions Page 8–91
- .3 Of Crores and Crores! — Figure it Out Page 91
- .4 Exact and Approximate Values — In-text Questions Page 101
- (Nearest Neighbours)1.4 Exact and Approximate Values — In-text Questions Page 11
- .4 Exact and Approximate Values — Estimating Sums and Differences Page 11–121
- .4 Exact and Approximate Values — Populations of Cities Page 131
- .5 Patterns in Products — In-text Questions Page 141
- .5 Patterns in Products — Figure it Out Page 141
- (How Long is the Product?)1.5 Patterns in Products — In-text Questions Page 14–15
- .5 Patterns in Products — Fascinating Facts about Large Numbers Page 16–181
- .6 Did You Ever Wonder…? — In-text Questions Page 18–191
- .6 Did You Ever Wonder…? — Figure it Out Page 19–211
- Puzzle Time — Puzzle Time: Toothpick Digits Page 23