Large Numbers Around Us

Overview

This chapter helps us read, write and make sense of very large numbers that appear around us, such as populations, distances and money. We learn the Indian and International place value systems and how to estimate large quantities.

Key concepts

• Place value: ones, tens, hundreds, thousands, lakhs, crores (Indian system).
• International system: thousands, millions, billions.
• Reading numbers with the help of periods and commas.
• Comparing, ordering and rounding off large numbers.
• Estimation to check whether an answer is reasonable.

Important formulae

• 1 lakh = 100 thousand = 1,00,000
• 1 crore = 100 lakh = 1,00,00,000
• 1 million = 10 lakh; 1 billion = 100 crore

Solved example

1. Write 3,45,672 in words (Indian system).
2. 3,45,672 = Three lakh forty-five thousand six hundred seventy-two.
3. Round it to the nearest thousand: the digit after thousands is 6, so 3,45,672 ≈ 3,46,000.

Important questions

1. Write 90,05,021 in words in both systems.
2. Arrange 1,23,456; 12,34,560; 9,99,999 in increasing order.
3. How many thousands make ten lakh?
4. Estimate the sum 4,98,000 + 3,02,500 by rounding to the nearest thousand.

Quick revision

Group digits into periods, read using lakh/crore (Indian) or million/billion (International), and use rounding to estimate. Estimation keeps large calculations quick and sensible.