Not as Hungry Anymore: Subtraction Up to 20

Imagine someone wants to buy 15 buns, but then at the last second, she says, “Actually, can you take out 8 buns? I’m not that hungry after all.”

How many will be left? This is the subraction problem 15 – 8, right? Hmm, well, here are the 15 buns we start with:

And now we’re going to take away 8 buns, right? Okay. First, let’s cross out the 5 buns that are in their own tin. I mean, who wants an extra empty tin lying around anyway? Okay, we’ve gotten rid of 5, so how many more do we need to cross out to take away a total of 8? We need to get rid of 3 more, since 3 + 5 = 8! See what I mean?

After crossing off 3 from the full tin, we’re left with just 7 buns. We can also imagine crossing off buns from the tins, or even use our fingers to cover them up—whatever you like the most. This is a great way to think about these problems and to practice mental math!