Homeschool Buyers Co-op is running a 40% off sale for the large Math Mammoth bundles. The offer expires 8/31/2020.

^

# Mental math: add and subtract multiples of ten

In this mental math lesson, we look at adding and subtracting multiples of ten (20, 30, 40, 50, etc.) to/from a 3-digit number mentally. It is very easy!

First, we do a few of these addition and subtraction problems with the help of a visual model - to show clearly that it is based on place value: we simply add the tens to the existing tens.

Then we solve some more challenging problems, a word problem involving Mathy, my mammoth mascot, and lastly we look at a number pattern of sorts.

If you cannot see the video above, click here for an alternative video player.

Mental addition - add a 2-digit and a 1-digit number (with regrouping)

Number rainbow & fact families with 12

Back to 2nd 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!

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)

### "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!

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)