Start here

A truck stops below the terrace. A man on the terrace shouts a number of bricks. It is too big to say back easily.

That is Part I, Chapter 1 of your book. It is Large Numbers Around Us. Let's count some bricks first.

What this track covers

• New columns past the thousand: ten thousand, lakh, crore.
• Two ways to place commas in the same number.
• Reading a big number out loud.
• Comparing two big numbers, without reading every digit.
• Rounding, and estimating before you compute.
• How big a lakh and a crore really are.
• Which way to round: up, down or exact.
• Estimates you know are above or below the real answer.
• Quick ways to multiply by 5, 25 and 125.

Quick catch-up

These earlier lessons help.

• Place value (Track Zero) — a digit's place tells its worth.
• Comparing numbers (Track Zero) — the number with more digits is bigger. If the digit counts match, compare digit by digit from the left.
• Biggest and smallest (Number Play) — put the biggest digit first. A zero at the front adds no value.
• A good estimate (Number Play) — round the numbers on purpose, then add.