Classroom tools
Part-part-whole model
Those parts don’t add up to the whole.
Type the missing number into the dashed box: it turns green when it’s right. In Make your own, tap a box to type any number, then choose a number to hide. If you leave the hidden box empty, it works out the answer for you.
About this part-part-whole model
A part-part-whole model shows how a number (the whole) splits into two parts. This free interactive version works on whiteboards, laptops and tablets. Choose the cherry (circles) or bar model, get random missing number questions to 10 or 20, or type in your own numbers and hide whichever one you like. Turn on counters to show each number as dots.