Missing Number
One number in the sentence is hidden. Work out which one it is — first with adding, then taking away, then times and divide. The gap does not always sit in the same place, which is the part that makes you think.
No account, and the maths stays in your browser — more— less
This activity is for learning and practice. Anything it suggests is indicative only — it is not a formal assessment and not a substitute for a teacher or tutor.
Nothing you answer is sent to Zerdly. Progress is saved on this device only if you switch saving on, and you can delete it at any time. How Kids Maths handles data.
Set your country and age — change
Setting an age keeps the questions at the right level for that age. It does not lock anything — you can still try any topic, at any age, in any order. Levels are a guide only, not a curriculum.
Your age is not saved anywhere. Your country is remembered only if you have switched saving on.
Saving your progress
Nothing is being saved. You can practise as much as you like — when you close the tab, the session is gone.
The sign you can see is not the sign you need
That is the whole trick. In ? + 7 = 12 the sign says add, but to find the missing number you take away. Adding and taking away undo each other, and so do times and divide — so whatever operation you can see, the one you have to do is its opposite.
Where the gap sits changes everything
Compare ? − 4 = 6 with 10 − ? = 6. Both are take-aways, and they need different things done to them. In the first, the missing number is the one you started with, so it has to be bigger than 6 — you put the 4 back on and get 10. In the second, the missing number is what was taken away, so you work out how far it is from 6 back up to 10 and get 4.
A child who has learned “missing number means do the opposite” gets one of those two wrong every single time, which is why this tool moves the gap around instead of keeping it in the same place.
Why it is worth practising on its own
Because it is algebra, before anybody says so. A letter in an equation is only a missing number with a name, and a child who is comfortable finding the gap in 4 × ? = 28 has already done the thinking that 4n = 28 asks for. The notation arrives later; the idea can arrive years earlier.
School levels
School levels are a guide only. They show where a skill is usually taught in each country and are not taken from, aligned to, or endorsed by any curriculum authority. Your school may cover it earlier or later.