Bar model
Your own numbers
Change the whole or a part and the bars resize to match. The missing number (striped) works itself out. Pick which number is missing by tapping it in the bar model.
Tap any box to make it the missing number. Children type the missing number and press Check, or you can press Reveal.
About this online bar model
The bar model shows the whole on the top bar and its parts underneath, drawn to scale so children can see how the numbers fit together. This free bar model tool makes missing number questions for addition and subtraction. Make a random question to 10, 20, 50, 100 or 1,000 with two, three or four parts, or type your own numbers and watch the bars change length to match. Tap any box to hide it, then children work out the missing part or the whole and check their answer.