Learning Objectives

• Understand the concepts of large numbers such as lakhs, crores, and arabs.
• Read and write large numbers in both Indian and American naming systems.
• Round large numbers to the nearest thousand, lakh, or crore.
• Factorise numbers and regroup them to simplify multiplication.
• Explore patterns in multiplication and develop quick calculation strategies.
• Estimate sums and differences of large numbers.
• Apply knowledge of large numbers to real-world scenarios and thought experiments.

Large Numbers

Indian and American Naming Systems

• 1 lakh: 1 followed by 5 zeroes: 1,00,000
• 1 crore: 1 followed by 7 zeroes: 1,00,00,000
• 1 million: 1 followed by 6 zeroes: 1,000,000 (which is also ten lakhs)
• 1 arab: 1 followed by 9 zeroes: 1,000,000,000 (which is also 100 crore or 1 billion)

Rounding Large Numbers

• We generally round up or round down large numbers to get a rough estimate of their size.

Factorization and Simplification

• We can factorize numbers to make multiplications simpler.

Examples of Large Numbers in Different Systems

Nearest Neighbours of Large Numbers

• For the number 6,72,85,183:
  • Nearest thousand: 6,72,85,000
  • Nearest ten thousand: 6,72,90,000
  • Nearest lakh: 6,73,00,000
  • Nearest ten lakh: 6,70,00,000
  • Nearest crore: 7,00,00,000

Thought Experiments

• Example: Would one be able to watch 1000 movies in a year?

Creative Challenges

1. Make exactly 30 button presses to achieve the largest and smallest 3-digit numbers.
2. Find different ways to achieve the same number using a calculator with specific buttons.