Idea 15of 23Builds onAdd in any order
Subtraction undoes addition
How does an addition fact give you a subtraction fact?
Today you'll discover
- one bar, four facts
- how to undo adding
- how to check a subtraction
Think first36 250 + 8 750 = 45 000
36 250 + 8 750 = 45 000. What is 45 000 − 8 750?
Decide first, then press Next. Find the whole and its two parts.
A bar of 45 000 split into 36 250 and 8 750. A second bar shows the 8 750 piece dashed and taken off, with 45 000 − 8 750 under the piece that is left. Then four sentences: two additions and two subtractions with 36 250, 8 750 and 45 000. The last step shows 27 400 + 5 600 = 33 000.
See the whole ideathe big idea and the key word, in one place
The big idea
Subtraction undoes addition: the whole minus one part is the other part.
A fact family
One bar, four facts.
36 250 + 8 750 = 45 0008 750 + 36 250 = 45 00045 000 − 8 750 = 36 25045 000 − 36 250 = 8 750
Key words
- inverse operations
- two operations that undo each other, like adding and subtracting
- fact family
- the addition and subtraction facts made from the same three numbers
Ready to use it?
- Write the subtraction facts that go with an addition.
- Check a subtraction by adding.