Big Whole Numbers
Primary 5 · Mathematics
Big Whole Numbers
Lesson 1 of 3
13 min
Let's begin
Mugisha's class is finding out how many people live in their district. The teacher turns to the board and writes one number: 372,458.
The class goes quiet. Everybody there can count to a thousand. But how do you even say a number like that without getting lost in the middle of it?
By the end of this lesson you will read it out loud without blinking — and write it, and pull it apart.
Look at 4,236. You can already read that: four thousand, two hundred and thirty-six.
You can read it because each digit sits in a place, and each place is worth ten times the place on its right:
Big numbers do not change the rules. They just keep the same pattern climbing:
Here is 372,458 sitting in its chart:
| Hundred thousands | Ten thousands | Thousands | Hundreds | Tens | Ones |
|---|---|---|---|---|---|
| 3 | 7 | 2 | 4 | 5 | 8 |
| 300,000 | 70,000 | 2,000 | 400 | 50 | 8 |
Go digit by digit, from the left:
Written out, that is the expanded form:
372,458 = 300,000 + 70,000 + 2,000 + 400 + 50 + 8
Add it back up to prove it: 300,000 + 70,000 = 370,000. Add 2,000 and you have 372,000. Add 400, then 50, then 8, and you land exactly on 372,458. It works.
People mix these two up all the time, so hold them apart.
In 372,458, the digit 7:
A digit on its own is small. What makes it big or small is where it stands.
The comma is your friend. It cuts the number into two halves:
372 | 458
Read the left half like an ordinary three-digit number, then say the word thousand. Then read the right half.
372,458 is three hundred and seventy-two thousand, four hundred and fifty-eight.
Try another: 60,409. Left of the comma is 60, so that is "sixty thousand". Right of the comma is 409, so that is "four hundred and nine". Together: sixty thousand, four hundred and nine.
Write ninety thousand and eight in figures.
But careful — the part after the comma must always be filled to exactly three digits. Eight is not 8, it is 008.
So the answer is 90,008. Not 90,8, which means nothing at all.
Take 405,006. Its zeros are holding three places empty: the ten thousands, the hundreds and the tens.
405,006 = 400,000 + 5,000 + 6
If you got lazy and dropped the zeros you would write 456 — a number thousands of times smaller. Every zero is doing a job: it keeps the other digits standing where they belong.
Keep counting: 999,997 … 999,998 … 999,999 … and now what? Every place is full. There is nowhere left to put one more.
So a brand new place opens on the left, and you write 1,000,000.
One million is a thousand thousands. In figures it is a 1 followed by six zeros — seven digits in total.
Tip
Cover the comma with your finger. Read the left part like a small number and add the word "thousand". Then move your finger and read the right part. Any six-digit number becomes two easy small numbers.
And when you write from words, the part after the comma always needs three digits — pad it with zeros. "Ninety thousand and eight" is 90,008.
Do each one in your exercise book, then tap Show answer to check.
What is the value of the digit 6 in 165,320?
Answer: 60,000. Count the places from the left: 1 is in the hundred thousands, so the 6 is in the ten thousands place. Six ten-thousands is 60,000.
Write 208,070 in words.
Answer: two hundred and eight thousand and seventy. Left of the comma is 208 (two hundred and eight thousand); right of the comma is 070, which is just seventy.
Write in figures: seven hundred and thirty thousand, five hundred and four.
Answer: 730,504. The thousands part is 730. The part after is five hundred and four, which fills three digits as 504.
Write 640,309 in expanded form.
Answer: 600,000 + 40,000 + 300 + 9. There is a 0 in the thousands place and a 0 in the tens place, and zero of something adds nothing, so those two do not appear in the sum — but they must still be written inside the number.
Which is worth more: the 9 in 90,415, or the 9 in 519,000?
Answer: the 9 in 90,415. There it sits in the ten thousands place and is worth 90,000. In 519,000 the 9 sits in the thousands place and is worth only 9,000. Same digit — very different value, because the place decides.
What you learned today
Quick check
What is the value of the digit 4 in 548,210?
