## Monday, April 15, 2013

### Multiplication....sigh.....

My kids have such a hard time with multiplication of multi-digit numbers because of all of the steps to remember.  I found a new method to teach kids how to multiply multi-digit numbers in a snap.  Don't believe it?  I didn't either, but I was willing to try anything.

Traditional multiplication has so many steps involving multiplying, adding, and place value.  It's just too much for my kiddos.  So, I went searching and found a new method!

Not only does it work, but the kids LOVE it!  Here's a brief summary of how it works.  I will warn you, since you learned to multiply "the old way"  it may take your brain a few tries to understand this method.

Step 1:  Change the way you write the problem.  Let's use the problem 54x72

Step 2:  Simple multiplication.  You will multiply 7x5 and put the answer in the first box.  The slash separates the tens and ones.  Then you multiply 7x4.  It will look like this.
You continue to the second row and multiply in the same manner.  2x5 and 2x4.  Since 2x4=8, you will need to put a 0 in the tens place.  It will look like this when you are finished multiplying.
Step 3:  Add on the diagonal.  I give the kids a sticky note to help them block off numbers they are not adding to help keep them from getting distracted from extra numbers.
We begin adding at the bottom right.  This number will be the ones place.  8

Next add 0+0+8=8 (Tens place)

Next add 1+5+2=8  (Hundreds place)

The 3 is moved to the thousands place.  The final answer is 3, 888.

Let's do another one.  78x45  This is what it looks like after you multiply.

Now, you add.  This time, we will need to "carry" since our sums will be more than 9.  Starting with the bottom left, the ones place is 0.

The tens place is 1 carry 1 ten over (5+4+2=11)  Here's the only tricky part.  Write the 1 down in the tens place for your answer and carry 1 up to the next row.

The hundreds place is 15 (3+8+3+1)  Here's the only tricky part.  Write the 5 down in the hundreds place for your answer and carry the 1 up to the next row.  Here's what it looks like.

Finally, you add 2+1.  3 is the thousands place.  The final answer is 3,510

Pretty cool, huh?  I have a step by step smartboard file that you can use to teach your class this method. You can find it HERE if you are interested.

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1. Love this! My kids also really struggle with double digit multiplication! I'll have to give this a try!

- Sasha
The Autism Helper

1. Oh, good! I hope it helps your kiddos!

2. What a GREAT idea!!!!!

Thanks for sharing!

Cynthia

3. Karla - Am I wrong or on your last example (the one you have to carry), isn't the box with 5x7 supposed to be 3/5, not 3/0? Or am I missing something?
- Tracy

4. Karla - Am I wrong or on your last example (the one you have to carry), isn't the box with 5x7 supposed to be 3/5, not 3/0? Or am I missing something?
- Tracy

1. You are absolutely correct. Sorry about the mistake. I guess I shouldn't blog after an all-nighter with my little one. Guess I'm not as young as I used to be. Thanks so much for catching my mistake. I'm fixing it now. :)

5. LATTICE MULTIPLICATION!

My 3rd graders love this method, as I too struggled to get them to learn the "traditional way". The way my math series teaches this skill you would write 54 across the top, and 72 down the right side. When you do it this way, then you can add down the diagonals and your answer can be put on the outside of the box.

I began teaching my students the partial products way as well, where in the problem 254x8 you would break the problem down:
200(8) 1600
50(8) 400
4(8) 32
_____ _____
2,032
together to get

Also I go through the traditional way, but my students seem to get lost when it comes to multiplying by the second digit.

Alyson

6. I am not a fan of lattice multiplication. I think for special education students, learning through musical songs can be beneficial. I recall one that had a nice steady beat to it an flowed. That was several years ago though. If you have a chance please check out my blog @ http://elementaryspecialeducation.org

7. Hi! I have a give away on my blog! Be sure to enter to win 2 products from my TPT store :)

The Adventures of Room 83

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9. Thank you for showing us that there is always something new to learn! We thought we had multiplication down over here but your new method caught us by surprise! We love your blog, keep it up! Sincerely, Ana from www.BioBubblePets.com