Subtraction table to 20

About this chart

Subtraction charts are rarer than addition charts, and the reason is that half the grid would hold negative numbers. This one is cut to the triangle that makes sense for a young child: every row stops where the answer would fall below zero, so nothing on the page needs explaining away.

Read across a row and the countdown is obvious — 12−1, 12−2, 12−3 each step down by one. Read down a column and the answers step up instead. Those two directions are the same fact family seen from either end, and a child who can move both ways on this chart is close to not needing it.

Look for a row's last filled square and you have found what a number takes away to reach zero. Sitting beside it is the fact that a number minus itself is nothing, which is much easier to see on a chart than to be told.