Use the Subtraction Facts I Know chart to discuss some of the patterns on the chart.
- What happens to the top numbers in each row as you read across from left to right? (They increase by one.)
- What happens to the top numbers in each column as you read down from top to bottom? (They increase by one.)
- What do you notice about the numbers you subtract in each row? (In each row, the number you subtract is the same.)
Explain that the Subtraction Facts I Know chart
includes some subtraction facts with zero that are not
on the Triangle Flash Cards. Discuss strategies for facts with zero.
- What do you know about subtracting zero from a
number? (The number does not change because
you are taking away nothing.)
- Look at the first column. What do you notice about
the facts? (They all have zero for an answer.
When you subtract two of the same numbers the
answer is zero.)
- If any number minus zero is that same number,
what is 6 − 0? 9 − 0? 21 − 0?
- If any number subtracted from itself is zero, what
is 7 − 7? 10 − 10? 34 − 34?
Have students circle the facts in the first row and
first column if they understand the strategies for subtracting
zero and subtracting any number from itself.
