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Standard place value and column mechanics
Numbers up to 7 digits: identifying values, and multiplying and dividing by 10, 100 and 1000.
Numbers are made from ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. With just those ten, you can write any number you like, from 7 to 7 million.
The secret is where each digit sits. In this lesson you will learn:
- what each digit in a number is worth
- how to read and write numbers up to 7 digits long (millions)
- how to compare big numbers and put them in order
- what happens to the digits when you multiply or divide by 10, 100 and 1000
1. Every digit has a job
Look at the digit 2 in each of these numbers:
- In 52, the 2 is worth 2.
- In 325, the 2 is worth 20.
- In 4,207, the 2 is worth 200.
Same digit, different place, different value.
Each place is called a column. For numbers up to the millions you need seven columns. Start from the right:
| Column | Short name | A 1 here is worth |
|---|---|---|
| Ones | O | 1 |
| Tens | T | 10 |
| Hundreds | H | 100 |
| Thousands | Th | 1,000 |
| Ten thousands | TTh | 10,000 |
| Hundred thousands | HTh | 100,000 |
| Millions | M | 1,000,000 |
We put the columns side by side in a place value chart. Here is 3,584,061. The 8 is in the ten thousands column, so it is worth 80,000.
Build a number: press ▲ and ▼ to change the digits
3,584,061
three million, five hundred and eighty-four thousand and sixty-one
- Tap any digit in the chart to see what it is worth.
- Make the biggest number the chart can hold. Then make one million.
- Make a number with a 0 in the middle. Tap the 0. What job is it doing?
2. Each column is worth 10 times more
- 10 ones make 1 ten.
- 10 tens make 1 hundred.
- 10 hundreds make 1 thousand.
- And so on, all the way up: 10 hundred thousands make 1 million.
Slide the 1 to the left and watch it grow
1,000
1 thousand is 1,000. That is the same as 10 hundreds.
3. Reading big numbers
Each group has a name. From the right: the ones, the thousands, then the millions.
How to read a big number
- Find the commasNo commas? Count three digits from the right and put one in. Count three more and put another.
- Read the first group, then say its name“three million”
- Read the next group, then say its name“five hundred and eighty-four thousand”
- Read the last group on its own“and sixty-one”
Example: read 3,584,061
3,584,061
- 3 → three million
- 584 → five hundred and eighty-four thousand
- 061 → sixty-one
Put the commas in: tap the gaps between the digits
4. Writing numbers from words
This is where lots of children slip up. Try it: write four thousand and six.
It is tempting to write 406. But 406 is four hundred and six. Four thousand needs four columns, so draw them first:
The answer is 4,006. The two zeros are doing an important job: they keep the 4 in the thousands column and the 6 in the ones column.
How to write a number from words
- Find the biggest part of the number“four thousand” means you need the thousands column.
- Draw the columns from there down to the ones
- Put each digit in its column
- Fill every empty column with a 0
Example: two million, forty thousand and nine
Make the number: drag the digits into the chart
- Drag a digit onto a column. Or tap a digit, then tap a column.
- Tap a column with a digit in it to empty it again.
5. Comparing and ordering numbers
How to compare two numbers
- Count the digitsA whole number with more digits is always bigger. 100,001 is bigger than 99,999.
- Same number of digits? Line them up and start on the left
- Stop at the first column that is differentThe number with the bigger digit there is the bigger number.
Example: which is bigger, 45,812 or 45,821?
- Ten thousands: 4 and 4. The same.
- Thousands: 5 and 5. The same.
- Hundreds: 8 and 8. The same.
- Tens: 1 and 2. Different! 2 is bigger.
Two symbols help you write it down:
- < means is less than: 45,812 < 45,821
- > means is greater than: 45,821 > 45,812
The open side always faces the bigger number, like a hungry crocodile. The point aims at the smaller one.
To put a list in order, find the smallest number first, then the next smallest, and so on. Ascending order means smallest first. Descending order means biggest first.
Which is bigger? Pick < or >
Put them in order: drag the cards, smallest at the top
- Drag a card up or down. Or use its ▲ and ▼ buttons.
The number display: drag digits in, out and around
- Drag a key into the display. Drop it in any gap, or at either end of the number.
- Drag a digit in the display to move it somewhere else. Drag it off the display to take it out.
- No dragging? Tap a key or a digit, then tap a gap. Del takes out the digit you picked.
- Put a 0 between the 7 and the 8. How do the words change?
- Move the 4 to the very end. Is the number bigger or smaller now? Which column decided it?
- Add a digit on the far left. What happens to the column of every other digit?
- Can you make the display say four million, five hundred and seven thousand, eight hundred and ninety-one?
6. Multiplying and dividing by 10, 100 and 1000
| Calculation | Zeros | The digits move |
|---|---|---|
| × 10 | 1 | 1 place left |
| × 100 | 2 | 2 places left |
| × 1000 | 3 | 3 places left |
| ÷ 10 | 1 | 1 place right |
| ÷ 100 | 2 | 2 places right |
| ÷ 1000 | 3 | 3 places right |
Example 1: 352 × 100
- 100 has two zeros, so every digit moves 2 places leftThe 3 moves from hundreds to ten thousands. The 5 moves from tens to thousands. The 2 moves from ones to hundreds.
- Fill the empty tens and ones columns with 0
Example 2: 46,000 ÷ 100
- 100 has two zeros, so every digit moves 2 places rightThe 4 moves from ten thousands to hundreds. The 6 moves from thousands to tens.
- The last two zeros move past the ones column and drop away
In this lesson every answer is a whole number. When a digit moves past the ones column, you need decimals. That is Lesson 1.2.
The place value machine: press a button and watch the digits move
352
- Press × 10 three times. Is that the same as pressing × 1000 once?
- Press × 100, then ÷ 100. Where do you end up?
- Try to divide 352 by 10. Why can’t the machine do it yet?
7. Working backwards
So if a question hides the start number, do the opposite to find it.
Example 1: ? × 100 = 34,000
- The opposite of × 100 is ÷ 10034,000 ÷ 100 = 340
Check: 340 × 100 = 34,000.
Example 2: how many hundreds are there in 45,600?
- “How many hundreds?” means “divide by 100”45,600 ÷ 100 = 456
Which button? Pick the one that turns the first number into the second
8. Practice: pick your level
Start with Foundation if you are in Year 4 or just starting. Move up when you are getting most of them right.
The mistakes that cost marks
- Leaving out a placeholder zero. Four thousand and six is not 406. draw the columns and put a 0 in every empty one: 4,006.
- Giving the digit instead of its value. In 3,584,061 the 8 is not worth 8. say which column it is in. The 8 is in the ten thousands, so it is worth 80,000.
- Counting the columns from the left. always start at the ones column, on the right.
- Comparing the first digits of numbers that are different lengths. 99,999 is not bigger than 100,001. count the digits first. More digits means bigger.
- Mixing up < and >. remember the open side faces the bigger number.
- Moving the digits the wrong way. remember that multiplying makes a number bigger, so the digits move left. Dividing makes it smaller, so they move right.
- Moving the wrong number of places. count the zeros: 10 is 1 place, 100 is 2 places, 1000 is 3 places.
Quick checklist
Tick each one when you can do it without help.
All ticked. Brilliant work! You have finished Lesson 1.1.
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