## Exploding Dots

### 8.3 Adding and Subtracting Decimals

Lesson materials located below the video overview.

Performing addition and subtraction with decimals in a $$1 \leftarrow 10$$ machine is no different from performing addition and subtraction in a $$1 \leftarrow 10$$ machine without decimals.

For example, here is a picture of $$22.37+5.841$$.

We see the answer $$2|7.11|11|1$$. Just add left to right and don’t worry about explosions!

With explosions we obtain an answer that society understand. We get 28.211. (Check this!)

And here is $$10.23-4.57$$.

We see the answer, after some annihilations, as  $$1|-4.-3|-4$$ . (Do you see this?)

Now with some unexplosions, we can fix up this answer for society to read. We get $$10.23-4.57=5.66$$. (Check that you follow this.)

Here are some practice questions you might, or might now, want to do.

11. What is $$0.05+0.006$$?

What is (0.05-0.006\)?

Can you see the answer with dots-and-boxes?

12.  Agatha says that computing $$0.0348+0.0057$$ is essentially the same work as computing $$348+57$$ in whole numbers. Do you agree?

Percy says that computing $$0.0852+0.037$$ is essentially the same work as computing $$852+37$$ in whole numbers. Do you agree?

## Books

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## Guides & Solutions

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