Difference Demonstrator

The Equal Addition Method

I made this resource after reading the wonderful Compendium of Mathematical Methods by Jo Morgan.

A tool for modelling subtraction as difference, but also for modelling how you can simplify a subtraction calculation by adjusting both the minuend and the subtrahend by the same amount.

e.g. 67 - 43

Add 3 to both (using your bonds of ten)

70 - 46 ... a much easier calculation in your head.

Things that you can move:

• the numberline
• the minuend
• the subtrahend

You can also reveal the difference by clicking on it or on the question mark.

Have fun!