Example 1
What number has 6 hundreds, 0 tens and 9 ones?
- 6 hundreds is 600, 0 tens is 0 and 9 ones is 9.
- 600 + 0 + 9 = 609. The 0 holds the tens place.
Answer: 609
🦘 Kangaroo Grade 3 · session 1 of 24 · 60 minutes · free
Kangaroo questions love digits: make the biggest number, count how many digits a book needs for its page numbers, find the missing digit. Learn what each place is worth and the tricks follow.
A complete lesson · 60 minutes
Open this page with your learner and work down it, or press Teach this lesson to go through it one step at a time on a big screen. Every section has something to do.
Grade 3 · ages 8 to 9 · contest level 3–4
Warm-up · think first
4 numbers: 407, 470, 704 and 740. A 3-digit number cannot start with 0, so only 4 or 7 can go first.
Teacher tip: Most learners say 6. Ask them to write every number down and check which ones are really 3-digit numbers.
Part 1 of 4 · learn, see, practise
Every digit has a value that depends on its place. In 374 the 3 is worth 300, the 7 is worth 70 and the 4 is worth 4.
A 0 keeps a place empty: 609 has 6 hundreds, 0 tens and 9 ones. Ten ones make a ten and ten tens make a hundred, so 15 tens is the same as 1 hundred and 5 tens.
What number has 6 hundreds, 0 tens and 9 ones?
Answer: 609
What number is 3 hundreds, 15 tens and 4 ones?
Answer: 454
Start with the warm-up and go as far as you can. The stretch questions are meant to be hard.
Part 2 of 4 · learn, see, practise
To make the biggest number from some digits, put the biggest digit in the biggest place, then the next biggest, and so on.
To make the smallest, put the smallest digit first, but never 0: a number cannot start with 0. Put the 0 straight after the first digit.
Make the biggest and the smallest 3-digit numbers from 5, 2 and 8.
Answer: 852 and 258
Make the smallest 3-digit number from 0, 6 and 3.
Answer: 306
Tap the cards to place them in order. Tap a placed card to take it back.
Start with the warm-up and go as far as you can. The stretch questions are meant to be hard.
Part 3 of 4 · learn, see, practise
The digit sum of a number is what its digits add up to: the digit sum of 507 is 5 + 0 + 7 = 12.
To count the digits needed to write many numbers, split them into groups: 1 to 9 use one digit each, 10 to 99 use two digits each.
What is the digit sum of 507?
Answer: 12
How many digits do you write to number the pages of a book from 1 to 25?
Answer: 41
Start with the warm-up and go as far as you can. The stretch questions are meant to be hard.
Part 4 of 4 · learn, see, practise
In a sum with missing digits, work one column at a time, starting with the ones. Remember a carry when a column adds to 10 or more.
When the same digit hides in two places, try the digits 0 to 9 and check. Kangaroo answers are only five choices, so testing each choice is a smart move too.
2☐ + ☐5 = 69. The same digit goes in both boxes. What is it?
Answer: 4
A 2-digit number has a tens digit 3 more than its ones digit, and its digit sum is 11. What is it?
Answer: 74
Start with the warm-up and go as far as you can. The stretch questions are meant to be hard.
Watch out
0 can never be the first digit. 0378 is really the 3-digit number 378.
In 374 the digit is 7 but its value is 70. Questions ask for one or the other: read carefully.
Page 25 needs two digits. Count the 1-digit and 2-digit pages separately.
Class activity 1 of 3
Use the digit cards 2, 5, 8 and 1, each once, to make 4-digit numbers.
Class activity 2 of 3
A book's pages are numbered 1, 2, 3, … with no gaps. Count the digits the printer needs.
Class activity 3 of 3
Each set of clues fits exactly one number. Find it.
After class · project
Make six puzzle cards about digits for someone at home, with the answer on the back.
What to make: Six cards with a puzzle on the front and the answer and working on the back.
Stretch: Make a clue puzzle whose answer is a 4-digit number and check that only one number fits.
| Look for | Done well when |
|---|---|
| Variety | Six different kinds of puzzle |
| Correct | Every answer is right |
| Working | The back of each card shows how to get the answer |
Copy it onto paper or print the practice sheet.
My digits: ___ ___ ___ ___ Card 1 (biggest): ____________________ Answer: ______ Card 2 (smallest): ___________________ Answer: ______ Card 3 (digit sum): __________________ Answer: ______ Card 4 (pages): _____________________ Answer: ______ Card 5 (secret number clues): ______________________ Card 6 (secret number clues): ______________________
Homework
Try each on paper, then tap to see the answer and working. Or print the practice sheet.
9876
91 (9 one-digit pages and 41 two-digit pages: 9 + 82)
299 (a hundreds digit of 1 would need 19 from two digits, which is too much)
6: 123, 132, 213, 231, 312, 321
36 (63 − 36 = 27)
🔥 Challenge round · finished early?
Cover the notes and try these from memory. They are meant to make you think hard: draw, try small cases, and check your answer.
How many digits are needed to number the pages 1 to 1,000?
Talk it through or use the drawing board. There is more than one way to get there.
Quiz · 8 questions
Pick an answer to see if it is right and why. Your best score is saved on this device.
🖨 Print what we learned
Pick what to practise, then print it or choose Save as PDF in the print window to download it.
For parents and teachers
Use it as it is, or stretch any part over two sessions. Each row links to the part of the page you need.
| Time | Part | The teacher | The learner |
|---|---|---|---|
| 0–4 min | Warm-up | Ask the warm-up question and wait for a guess before any hint. | Guess, then explain. |
| 4–12 min | Place value | Explain, reveal the examples one step at a time, then the practice. | Practise up to the stretch question. |
| 12–21 min | Biggest and smallest | Hand out digit cards, then use the on-screen cards for the tasks. | Practise; try the stretch. |
| 21–28 min | Digit sums | Explain and show the examples. | Practise. |
| 28–35 min | Missing digits | Explain and show the examples. | Practise; the stretch can be homework. |
| 35–42 min | Activity 1 | Let the learner work alone; hint only after a wrong check. | Solve and check. |
| 42–49 min | Activity 2 | Do the first item together, then let them finish. | Finish the activity. |
| 49–55 min | Activity 3 | Set as homework if time is short. | Solve the puzzles. |
| 55–59 min | Quiz | Run the quiz like the contest: no calculator, pick one of five answers. | Answer and read why. |
| 59–60 min | Set the project | Show the template and agree a due date. | Start the project. |
Use real digit cards and a place-value chart (hundreds, tens, ones) for every question.
How many digits are needed to number the pages 1 to 1,000?
FAQ
Making the biggest or smallest number from digits, digit sums, counting digits in page numbers and missing digits in sums. This lesson practises each kind.
Put the smallest digit that is not 0 first, then the 0, then the rest from smallest to biggest: from 0, 6 and 3 you get 306.
Yes, the first two lessons of the course are free to teach, with the practice sheet.
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