Large numbers are grouped in threes, separated by commas. Each group is a period.
Period is a group of three digits in a large number, like the thousands period.
Step 1: Picture It
Start with something you already know.
Reading a phone number
- A phone number is a long row of digits.
- Nobody reads it as one giant number.
- You read it in small groups, with a pause between.
A comma cuts a big number into groups you can read.
Where the picture stops: group in threes from the right, then say "thousand" at the comma.
Step 2: Let's Learn
Read it, or press Listen and follow the words.
Try it first
Ana looks at 3,470. How many digits sit after the comma?
Stuck is fine. Let’s Learn shows the way next. Got it first time? You can jump ahead to Watch an Example.
Read one period at a time
342,715 reads as "three hundred forty-two thousand, seven hundred fifteen".
Expanded form
342,715 is 300,000 + 40,000 + 2,000 + 700 + 10 + 5.
Zeros still hold places
In 40,006 the zeros keep the 4 and the 6 in their proper places.
Step 3: Try It Yourself
Tap and try it out.
Hundreds
7
Tens
1
Ones
5
seven hundred fifteen
700 + 10 + 5 = 715
7 hundreds, 1 ten and 5 ones is 715.
Step 4: In Real Life
A city’s population
A city has 254,000 people. Two hundred fifty-four thousand. Newspapers, road signs and forms all use numbers this big.
Step 5: Watch an Example
One step at a time.
Watch Ana Read 615,040
Ana reads 615,040 out loud, one group at a time.
- Step 1
Ana finds the comma. It splits the number into two groups of three.
Watch Leo Write a Number from Words
Leo hears "ninety thousand, three hundred six". He starts. You finish.
- Step 1
Leo hears two parts: ninety thousand, then three hundred six.
Step 6: Your Turn
Practice makes it stick.
Filling In the Form
Problem 1 of 12
A form asks for 200,000 + 40,000 + 3,000 + 50 in digits. What goes in the box?
The Road Sign
Problem 2 of 12
A road sign says a town has 108,004 people. How do you read that number?
Read It and Write It
Split at the comma first. Then take one group at a time.
Problem 3 of 12
What is "seventy thousand, six hundred" in digits?
Problem 4 of 12
In 384,205, what is the 8 worth?
Problem 5 of 12
Where does the comma go in 428631?
Find the Mistake
One line on each page is a slip. Find it, then fix it.
Problem 6 of 12
Dev writes "sixty thousand, four hundred five" in digits. One line is a slip. Which?
Dev's answer for: sixty thousand, four hundred five
- 1Thousands period: 60
- 2Ones period: 45
- AnswerSo the number is 6,045
Problem 7 of 12
What is "sixty thousand, four hundred five" in digits?
Problem 8 of 12
Maya reads 70,308 out loud. One line is a slip. Which?
Maya's answer for: how is 70,308 read?
- 170,308
- 2First group: seventy thousand
- AnswerLast group: thirty-eight
Problem 9 of 12
In 70,308, what is the 3 worth?
Same Number?
Pick every one that shows the same number. There is more than one.
Problem 10 of 12
Which of these show the same number as 30,208?
Problem 11 of 12
Which of these show the same number as 400,000 + 7,000 + 60?
Build a Period
Build it, then check.
Problem 12 of 12
Build the ones period of "sixty thousand, nine hundred four".
Nothing.
Hundreds
0
Tens
0
Ones
0
0 hundreds, 0 tens and 0 ones is 0.
Step 7: Quick Check
Show what you know.
Question 1 of 2
60,000 + 700 + 8 in digits?
Question 2 of 2
What does a comma do in a large number?
Ready for more?Optional. Past the lesson, for anyone who wants it.
Stretch 1 of 2
Use the digits 1, 2, 3, 4, 5 and 0 once each. What is the smallest six-digit number you can write?
Stretch 2 of 2
A number has a 6 in the hundred thousands place. It has another 6 in the tens place. Every other place is 0. What is it?
What You Learned
- Large numbers are grouped in periods of three.
- Read one period at a time, then say its name.
- Expanded form shows what each digit is worth.
For the grown-up
This lesson is where the child reads and writes multi-digit numbers in numerals, words, and expanded form. Each place is ten times the one to its right, and that single rule generates the whole system all the way to a million and, later, all the way down past the decimal point.
Watch for large numbers read digit by digit. "Four hundred and seven thousand" is a structure; "four zero seven" is a phone number.
Have them say the number aloud before working with it. Most errors with big numbers are reading errors that the arithmetic then faithfully preserves.
The slip this lesson targets is a zero dropped out of a period: Dev writes "sixty thousand, four hundred five" as 6,045, because he gave the ones period two digits when it needs three. Ask how many digits a period holds before any are written, which is worth asking aloud. Maya's slip is the same fault while reading: 308 said as thirty-eight, with the zero skipped instead of held. Saying the number one group at a time, and naming the column each digit sits in, catches both.
Numbers are read in groups of three — The commas in 348,275 split the number into periods: 348 thousands and 275 ones. Read each group as an ordinary three-digit number and say the period name after it: "three hundred forty-eight thousand, two hundred seventy-five". The commas are a reading aid, nothing more.
Writing from words — To write "sixty thousand, four hundred five", build it period by period: 60 in the thousands period, 405 in the ones. That gives 60,405. The zeros are essential — they hold the empty places open, and leaving one out shifts every digit to its left.
Expanded form for large numbers — 348,275 is 300,000 + 40,000 + 8,000 + 200 + 70 + 5. Writing it out this way makes each digit's value explicit, and it is exactly the decomposition that column addition relies on. Expanded form is not busywork; it is the algorithm written honestly.
A note on the word "and" — In careful mathematical reading, "and" marks the decimal point, so 405 is "four hundred five", not "four hundred and five". Everyday speech uses "and" freely and no one will misunderstand you. Knowing the convention matters most when decimals arrive.
Read it in groups of three — 3 4 5 6 7 8. Split it from the right into threes: 345,678. Read the left group, then say its name: three hundred and forty-five thousand. Then read the last group: six hundred and seventy-eight. The comma is not decoration. It tells you where to breathe.