Year 1: Missing numbers
Part of the Year 1 adding and subtracting within 10 chapter. Chapter overview · whole chapter on one page · Download worksheet (PDF) · Answers (PDF)
Missing numbers
Sometimes a number is missing. We show the missing number with a box: ?.
The sentence 4 + ? = 9 asks: what number do we add to 4 to make 9? Start at 4 and count on until you reach 9. You count 5 steps, so the missing number is 5.
The box can be on the left, in the middle or on the right of the = sign. The sentence must still be true.
Key ideas
- A box means a missing number. Find the number that makes the sentence true.
- Count on to find a missing number in an addition sentence.
- Count back to find a missing number in a subtraction sentence.
- Check your answer by putting it back in the sentence.
Key words. A missing number is shown by a box. Find the number that makes the sentence true.
Method. Start at 6. Count on until you reach 10. The number of counts is the missing number.
- Start at 6, the number we know. Put your finger on it.Start: 6
- Count on to 10. Say each number as you count on.7, 8, 9, 10
- Count how many numbers you said. That many is the missing number.4 numbers
- Write the missing number. 4
Check. 6 + 4 = 10. ✓
Watch out. Count the numbers after 6, not 6 itself.
Key words. Adding undoes taking away.
Method. Undo the take away. Put back the number that was taken away.
- Look at the answer, 5. The answer is what is left after taking away.Answer: 5
- Add 2 back on. Adding undoes taking away.5 + 2 = 7
- Write the missing number. 7
Check. 7 − 2 = 5. ✓
Watch out. Do not take the number away again. Put it back on instead.
Key words. The box is the number we take away.
Method. Start at 8. Count back until you reach 3. The number of steps is the missing number.
- Start at 8. That is the number we begin with.Start: 8
- Count back to 3. Each step back takes one away.7, 6, 5, 4, 3
- Count how many steps you took. The steps are the number taken away.5 steps
- Write the missing number. 5
Check. 8 − 5 = 3. ✓
Watch out. Count the steps back. Do not count the number you start from.
Watch out
Watch out: a box on the left is still a missing number. Check your answer: 6 + 4 = 10 is true.
Exam tip
Grown-up tip. Put 6 counters on the table and ask: “How many more do we need to make 10?” Let your child add the counters one at a time, then write the sentence together.
Exercise 2E Missing numbers
Non-calculatorKey words. A missing number is shown by a box. Find the number that makes the sentence true.
Method. Start at 2. Count on until you reach 5. The number of counts is the missing number.
- Start at 2, the number we know. Put your finger on it.Start: 2
- Count on to 5. Say each number as you count on.3, 4, 5
- Count how many numbers you said. That many is the missing number.3 numbers
- Write the missing number. 3
Check. 2 + 3 = 5. ✓
Watch out. Count the numbers after 2, not 2 itself.
Key words. A missing number is shown by a box. Find the number that makes the sentence true.
Method. Start at 3. Count on until you reach 7. The number of counts is the missing number.
- Start at 3, the number we know. Put your finger on it.Start: 3
- Count on to 7. Say each number as you count on.4, 5, 6, 7
- Count how many numbers you said. That many is the missing number.4 numbers
- Write the missing number. 4
Check. 3 + 4 = 7. ✓
Watch out. Count the numbers after 3, not 3 itself.
Key words. The box is the number we take away.
Method. Start at 5. Count back until you reach 2. The number of steps is the missing number.
- Start at 5. That is the number we begin with.Start: 5
- Count back to 2. Each step back takes one away.4, 3, 2
- Count how many steps you took. The steps are the number taken away.3 steps
- Write the missing number. 3
Check. 5 − 3 = 2. ✓
Watch out. Count the steps back. Do not count the number you start from.
Key words. Adding undoes taking away.
Method. Undo the take away. Put back the number that was taken away.
- Look at the answer, 6. The answer is what is left after taking away.Answer: 6
- Add 2 back on. Adding undoes taking away.6 + 2 = 8
- Write the missing number. 8
Check. 8 − 2 = 6. ✓
Watch out. Do not take the number away again. Put it back on instead.
Key words. Adding undoes taking away.
Method. Undo the take away. Put back the number that was taken away.
- Look at the answer, 7. The answer is what is left after taking away.Answer: 7
- Add 2 back on. Adding undoes taking away.7 + 2 = 9
- Write the missing number. 9
Check. 9 − 2 = 7. ✓
Watch out. Do not take the number away again. Put it back on instead.
Key words. A missing number is shown by a box. Find the number that makes the sentence true.
Method. Start at 5. Count on until you reach 8. The number of counts is the missing number.
- Start at 5, the number we know. Put your finger on it.Start: 5
- Count on to 8. Say each number as you count on.6, 7, 8
- Count how many numbers you said. That many is the missing number.3 numbers
- Write the missing number. 3
Check. 5 + 3 = 8. ✓
Watch out. Count the numbers after 5, not 5 itself.
Key words. The box is the number we take away.
Method. Start at 6. Count back until you reach 2. The number of steps is the missing number.
- Start at 6. That is the number we begin with.Start: 6
- Count back to 2. Each step back takes one away.5, 4, 3, 2
- Count how many steps you took. The steps are the number taken away.4 steps
- Write the missing number. 4
Check. 6 − 4 = 2. ✓
Watch out. Count the steps back. Do not count the number you start from.
Key words. A missing number is shown by a box. Find the number that makes the sentence true.
Method. Start at 4. Count on until you reach 9. The number of counts is the missing number.
- Start at 4, the number we know. Put your finger on it.Start: 4
- Count on to 9. Say each number as you count on.5, 6, 7, 8, 9
- Count how many numbers you said. That many is the missing number.5 numbers
- Write the missing number. 5
Check. 4 + 5 = 9. ✓
Watch out. Count the numbers after 4, not 4 itself.
Key words. True means it is right. False means it is not right.
Method. Work out the sum, then check if the sentence is true.
- Work out 4 + 3. Count on from the bigger number.4 + 3 = 7
- Compare with the other side of the = sign. True means both sides are the same.7 and 8
- Write the answer. False
Check. Count all the things: 4 + 3 = 7. ✓
Watch out. The answer is False if the two sides are not the same.
Key words. The box is the number we take away.
Method. Start at 9. Count back until you reach 4. The number of steps is the missing number.
- Start at 9. That is the number we begin with.Start: 9
- Count back to 4. Each step back takes one away.8, 7, 6, 5, 4
- Count how many steps you took. The steps are the number taken away.5 steps
- Write the missing number. 5
Check. 9 − 5 = 4. ✓
Watch out. Count the steps back. Do not count the number you start from.
Key words. A pair is two numbers that go together.
Method. Find two different pairs that make 6. Any correct pair is fine.
- Try 1 and 5. Count on from the bigger number.1 + 5 = 6
- Try 2 and 4. A different pair that also makes the total.2 + 4 = 6
- Write the answer. Both pairs make the same total.1 + 5 = 6 or 2 + 4 = 6
Check. Count on to check each pair. Both give 6. ✓
Watch out. Make sure both numbers in your pair are different from the other pair.