Someone has worked a question out and got it wrong. These free printable worksheets show the wrong answer and ask for the right one, with room to say what went wrong.
If they get stuck
The answer key prints on a separate page.
Marking someone else's work is a different job from doing your own, and it is a harder one. A child solving a question chooses their own route; a child checking one has to follow somebody else's and find where it left the road. That is the skill every proof, every debugging session and every re-read of your own work depends on.
The errors are the ones children actually make — a digit carried that should not have been, a times table one out, an operation done in the wrong order. Recognizing a mistake as familiar is uncomfortable and useful, because a child who can name it in someone else's work starts catching it in their own.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Spot the error, step by step