Chapter 6: House of Hundreds – I

Imagine a house with three rooms , one for ones, one for tens, and one for hundreds. Every number has its own way of filling these rooms. Welcome to the House of Hundreds!

What we'll learn

• Read and write numbers up to 999.
• Understand the place value of each digit.
• Write numbers in expanded form.
• Compare three-digit numbers.
• Build numbers using place value blocks.

The big idea

A three-digit number has three rooms. The right-most room holds ones. The middle room holds tens. The left-most room holds hundreds. The digit in each room tells how many of that bundle are kept there.

Take the number 247. The 7 sits in the ones room , that means 7 single sweets. The 4 sits in the tens room , that means 4 packets of ten sweets each, or 40 sweets. The 2 sits in the hundreds room , that means 2 boxes of hundred each, or 200 sweets.

Adding them up: 200 + 40 + 7 = 247. This is called the expanded form of a number. It shows the full story.

When we compare two three-digit numbers, we first look at the hundreds. If the hundreds are equal, we look at the tens. If even the tens match, we look at the ones. Just like a queue , the tallest goes to the front first.

Let's explore

Place value cards. Cut paper strips and write 100, 200... 900 on big cards, 10, 20... 90 on medium cards, 1 to 9 on small cards. Lay them on top of each other to build any number.

Currency game. Use play notes of 100, 10 and 1 rupee. Pay 358 rupees using the fewest notes. Now pay 273 rupees.

Build and break. Pick any 3-digit number. Write it in expanded form. Now do the reverse , start with 600 + 80 + 4 and find the number.

Bus stops. Imagine 3 bus stops at km 245, km 287 and km 209. In what order will the bus pass them?

Worked examples

Example 1. Write 506 in expanded form.

• 5 in the hundreds room = 500.
• 0 in the tens room = 0.
• 6 in the ones room = 6.
• 500 + 0 + 6 = 506.

Example 2. What is the place value of 8 in the number 384?

• 8 is in the tens room.
• Its place value is 80.

Example 3. Which is bigger: 462 or 426?

• Both have 4 hundreds.
• 462 has 6 tens; 426 has 2 tens.
• 6 tens is more, so 462 is bigger.

Quick check

1. Write 729 in expanded form.
2. What is the place value of 3 in 537?
3. Which is smaller: 405 or 450?
4. Write the number that has 6 hundreds, 0 tens and 4 ones.
5. Arrange in order: 312, 213, 132.

Recap

• Every digit in a number has a place , ones, tens or hundreds.
• The expanded form breaks a number into hundreds + tens + ones.
• When comparing, start from the highest place.