The Difference Bar

Students explore mental strategies to calculate the difference between two numbers. The basic strategy employed is that the difference can be found by addition.

Teacher notes

  • A partitioning model is used to help students see the value of strategies such as rounding to 10, or compensating to the next 10 to help find the difference.
  • The animation at the commencement of the learning object demonstrates some of the strategies, which are also available as 'hints' while students work.
  • The printouts show how the student solved each equation.

Learning objects

The difference bar picture.

The difference bar: generate easy subtractions
The sums generated enable students to find the difference between a single-digit number and a double-digit number.