The gap between

Grades 3–4

The big idea

Subtraction can also mean: how far apart are two amounts?

Think of it like two towers, measuring the step between them: A tower of 8 and a tower of 5: the difference is the 3 extra blocks one has over the other.

Match them up

Stand a tower of 8 next to a tower of 5. Match them block-for-block. The blocks left sticking up on the taller tower are the gap. Here, 3.

Tap a block to take it away.

That's 3.

Wonder out loud

These are good questions to ask: yourself, a grown-up, or your math helper.

Ask your math helperon this device · private

Hi! I help you see why the math works. Tap a question to start: