Question 1
Solve 7 + ? = 10
Think: 7 and what make 10?
Year 1
Solve missing number problems such as 7 = ? - 9
Find the hidden number in an addition or subtraction sentence by using what you already know.
Lesson overview
Number - addition and subtraction
A missing number problem has one hidden part. We look at the numbers we know, decide whether the problem is about adding or subtracting, and then work out the hidden number. Sometimes the missing number is at the start, in the middle or at the end.
5 and what make 8?
5 + 3 = 8
What number goes with 4 to make 10?
6 + 4 = 10
9 and 7 make the starting number.
16 - 9 = 7
Worked example
Solve ? - 6 = 8.
Think about the starting number before 6 were taken away.
14 - 6 = 8
- Look at the numbers we know. 6 are taken away and 8 are left.
- Think about the whole before anything was taken away.
- Count on from 8 by 6, or use the fact that 8 and 6 make 14.
- The missing number is 14, so 14 - 6 = 8.
Try it
Look at the number sentence, decide what is hidden, then work it out.
Question 2
Solve ? + 5 = 12
What number goes with 5 to make 12?
Question 3
Which number makes this true: 14 - ? = 9
Think: what was taken away from 14 to leave 9?
Question 4
Solve ? - 4 = 11
4 and 11 make the starting number.
Question 5
What helps you solve a missing number problem?
Common mistakes
These reminders help when one number is hidden.
- Choosing one of the numbers already in the sentence instead of working out the hidden one.
- Using the wrong operation and adding when the problem is really about subtracting, or the other way around.
- Forgetting that the missing number can be at the start, not only at the end.
Related topics
These connect closely to missing number problems.
- Represent and use number bonds and related subtraction facts within 20.
- Add and subtract one-digit and two-digit numbers to 20, including zero.
- Solve one-step addition and subtraction problems using concrete objects and pictures.