^

# How to divide decimals by decimals - simple explanation and why it works

To divide by a decimal, first change the ENTIRE division problem to another with a whole-number divisor, yet with the same answer. How? Simply multiply both numbers in the division problem (the dividend and the divisor) by 10 repeatedly, until the divisor is a whole number. (The dividend doesn't matter; it can be a decimal).

The shortcut for multiplying by 10 is of course that you move the decimal point, and most school books only give you the shortcut, without explaining this principle for division of decimals that in reality, we are MULTIPLYING both the dividend & divisor by 10, 100, 1000 (powers of ten).

We can do this process, because in it, the answer (the quotient) does not change. Think about it: 0.2 goes into 0.7 as many times as 2 goes into 7, or 20 goes into 70. Similarly, if you have a division problem with a decimal divisor, such as 4.392 / 0.7, you're solving how many times 0.7 goes into 4.392. But that is the same as finding how many times 7 goes into 43.92.

This process works equally well whether we are using mental math to divide or long division.

Math Mammoth Decimals 2 — downloadable worktext

Back to 5th grade videos index

Back to the index of all videos

WAIT!

Receive my monthly collection of math tips & resources directly in your inbox — and get a FREE Math Mammoth book!

We respect your email privacy.
You can unsubscribe at any time.

### Math Mammoth Tour

Confused about the different options? Take a virtual email tour around Math Mammoth! You'll receive:

An initial email to download your GIFT of over 400 free worksheets and sample pages from my books. Six other "TOURSTOP" emails that explain the important things and commonly asked questions concerning Math Mammoth curriculum. (Find out the differences between all these different-colored series!)

This way, you'll have time to digest the information over one or two weeks, plus an opportunity to ask me personally about the curriculum.
A monthly collection of math teaching tips & Math Mammoth updates (unsubscribe any time)
We respect your email privacy.

Note: You will FIRST get an email that asks you to confirm your email address. If you cannot find this confirmation email, please check your SPAM/JUNK folder.

### "Mini" Math Teaching Course

This is a little "virtual" 2-week course, where you will receive emails on important topics on teaching math, including:

- How to help a student who is behind
- Troubles with word problems
- Teaching multiplication tables
- Why fractions are so difficult
- The value of mistakes
- Should you use timed tests
- And more!

You will also receive:

A GIFT of over 400 free worksheets and sample pages from my books right in the very beginning. A monthly collection of math teaching tips & Math Mammoth updates (unsubscribe any time)
We respect your email privacy.

Note: You will FIRST get an email that asks you to confirm your email address. If you cannot find this confirmation email, please check your SPAM/JUNK folder.

### Maria's Math Tips

Enter your email to receive math teaching tips, resources, Math Mammoth news & sales, humor, and more! I tend to send out these tips about once monthly, near the beginning of the month, but occasionally you may hear from me twice per month (and sometimes less often).

You will also receive:

• A GIFT of over 400 free worksheets and sample pages from my books.
We respect your email privacy.