The two tasks in this unit provide plenty of reinforcement for using a tidy number to solve subtraction problems. In the first activity students need to help Henry turn more than twenty 3 digit numbers into tidy numbers to they can fit through the subtraction machine. The second task is all about using tidy numbers to solve problems. An example is given that clearly shows how the same action needs to be performed on both numbers in a subtraction problem to calculate the difference more easily. Thirty eight questions occur across two pages.