In this lesson, students must become detectives to solve for the missing number in each subtraction problem. They will develop and use their powers of mathematical reasoning using number bonds to find differences.

This lesson focuses on facilitating a rich classroom discussion around the purpose and methods of rounding numbers up to the thousands place. It can be taught on its own or as support to the lesson Rounding with Number Lines.

Give your students a head start in rounding with this fun lesson that gives them an easy trick to help them learn if they should round up or down to the nearest 10.