Tens and ones, then hundreds

A ten is a bundle of ten ones, and a hundred is ten tens. What each digit is worth in a two-digit and a three-digit number, why a zero in the middle matters, and how to read blocks, expanded form and number names. Comparing with <, = and > by looking at the left digit first, ten more and ten less, and skip-counting by 5s, 10s and 100s. Study cards, hints, a practice quiz at three levels, and four workshop activities that check themselves.

Jump to another unit

Start Here

Start here

Ten of these make one of those

Ten single ones, loose on the table.

Two things people get wrong

People often think…

39 is bigger than 41, because 9 is bigger than 1.

People often think…

Three hundred six is written 36.

Read the places, left to right

Watch one

Which is bigger: 39 or 41?

Look at the tens first.
39 has 3 tens. 41 has 4 tens.
4 tens is more than 3 tens.
41 — even though 9 is bigger than 1.

One sentence, then you move on

Why do you look at the tens before the ones?

Your sentence

Where this goes

Where this lives

Street numbers, prices, a jersey number, page numbers — anywhere a digit's place is what tells you how big it is.

What this feeds

Next unit is adding and subtracting within 1,000, where bundles get traded back and forth.

Find a number with three digits near you and say what each digit is worth.

Your answer

Next: Adding and Subtracting within 1,000 →

Helpful Hints

⚖️ Comparing two numbers — the three steps

Count the digits: more digits means a bigger number → same number of digits? Look at the LEFT digit first (hundreds, then tens) → the first place where the digits are different decides it; the bigger digit there means the bigger number. Only look at the ones if everything to the left matches.

Left digit first. Stop at the first difference.

💡 The whole topic in one idea

Every place is worth TEN of the place to its right. Ten ones make a ten; ten tens make a hundred; ten hundreds make a thousand. A digit tells how many of that place you have, and the place tells what each one is worth.

Ten of these make one of those.

⚠️ Traps the test loves

Comparing the ones first: saying 39 > 41 because 9 > 1. Tens first, always.
Dropping the zero: writing “three hundred six” as 36. The 0 holds the tens place: 306.
Swapping the places: 4 tens and 3 ones as 34. Tens on the left: 43.
Adding the digits instead of their worth: 243 = 2 + 4 + 3. It is 200 + 40 + 3.
Counting the pieces, not the amount: 2 tens and 12 ones is 32, not 14 and not 212.
Ten more as one more: ten more than 47 is 57, not 48. The ones digit does not move.

🏢 The places — the chart

Place	Block	Made of	In 243, the digit is worth
Ones	a small cube	1	3 ones = 3
Tens	a rod	10 ones	4 tens = 40
Hundreds	a flat square	10 tens = 100 ones	2 hundreds = 200
Thousands	a big cube	10 hundreds	— (243 has none)

🎯 How the test will ask

A picture of blocks — “What number?” Count flats as hundreds, rods as tens, cubes as ones; write a digit for every place.
A number with one digit underlined — “What is it worth?” Name the place, then say how many of it.
Two numbers and a blank — “<, = or >?” Left digit first; the mouth eats the bigger number.
Three or four numbers — “Order from least to greatest.” Count digits, then compare place by place.
A number in words — “Write it with digits.” Listen for the hundreds, the tens, the ones; put a 0 where nothing is said.
A pattern — “230, 240, 250, __.” Find the jump: by 5, by 10 or by 100; only one digit should change.
Expanded form — “243 = __ + __ + __.” One piece per place, each worth its place.

✅ Before the test, can you…

Say what a ten and a hundred are made of?
Name the place and the worth of any digit in a three-digit number?
Read a picture of blocks and write the number, even with a zero in the middle?
Write a number in expanded form and from its name in words?
Compare two numbers with <, = or >, tens before ones?
Find ten more, ten less, a hundred more and a hundred less without counting?
Skip-count by 5s, 10s and 100s from any starting number?