What remains: subtraction

Find what remains after taking away and compare differences by pairing.

An idea to revisit first: Count together: addition →

Think with objects in front of you

Mark the objects taken away, then count only those that remain.

Take two marbles from five. If we ask how many remain, we count the three left, not the two removed. Write 5−2=3.

The sign − means subtraction. Distinguish the starting amount, amount removed and amount remaining. Put the removed two back with the three: five returns.

Subtraction also describes a difference. Pair a group of five with a group of two. Three remain unmatched: five is three more than two.

Here we do not remove more objects than we have. Negative numbers later extend subtraction. For now, examine situations with nonnegative remainders.

Listen one paragraph at a time

1/4

2/4

3/4

4/4

Now move the objects yourself

Choose the starting count and the amount removed. Crossed objects are removed. Count the uncrossed objects before revealing the answer.

Tap objects to mark what you have counted. There is no time limit.

Starting count5

Number removed3

You may use small toys or blocks instead of the screen. Explain what stayed the same and what changed.

Check your idea with different examples

You give away three of eight stickers. How many remain?

Match seven blocks with five, one to one. What is the difference?

How can addition check the remaining amount?

You may speak or draw on paper. Look for these ideas in your explanation.

I distinguished removed objects from remaining objects.I combined remaining and removed amounts to check the original.

Continue reading, or pause here

Grouping objects in tens makes larger counts easier to read. Continue to place value.