**Place value slides** are a fantastic resource to teach what happens when numbers are multiplied or divided by a power of 10 (10, 100, 1000 or 0.1, 0.01, 0.001, etc.). The “traditional” method of teaching students to “move the decimal point” is crap, and should *NEVER *be taught. But to listen to lots of young adults (such as many of my preservice teacher students), that is exactly what they have been told. And unless they understand what I teach in this video, that’s what *their *students will learn.

Decimal points do **not **move. Ever. Even in a bad math lesson. The decimal point exists to separate ones from tenths, or whole number places from decimal fraction places. Telling students to move the decimal point is like asking them to rearrange the letters of the alphabet because it happens to suit the teacher’s strange ideas of alphabetical order.

Use a place value slide to demonstrate the “shifting” of every digit left or right as a number is multiplied or divided by a power of ten. Making a place value slide involves use of a sharp knife, and so should be done by an adult. But the effort is worth it in demonstrating clearly what happens within the base ten system when multiplying by a power of ten, such as when converting metric measurements or calculating with percentages.

## Download:

- Place Value Slide & Worksheets – PDF file containing Place Value Slide template and 8 worksheets with Answer Keys, ready to use with your class to teach multiplication and division by powers of ten.

Please leave a comment below – the feedback will help us plan future podcast episodes!

JudithApril 10, 2012 at 11:06 AMTo move the decimal point was the way I was taught. 🙂 A more multisensory way of teaching is to allocate students a digit with one student being the decimal point and then having the students do the “sliding” and the decimal point stays still.

What i find is that students do not understand that our place value system is based on the power of 10. No matter how much work is done with MAB blocks etc they just don’t seem to understand that. Until that is firmly understood they will always have problems with multiplication and division by powers of 10.

Peter PriceApril 10, 2012 at 11:28 AMI agree with you 100%, Judith!

Most children (indeed, most adults) don’t appear to really understand the powers of 10 basis for our numeration system. As a result, the question of moving digits or moving the decimal point is rather unimportant.

The idea of having students hold up numerals and a decimal point, and model the multiplication or division process is a great one.

Thanks for your contribution!

SandraSeptember 8, 2012 at 12:00 AMCould not download the place value slide and worksheet. How can I get this?

Peter PriceSeptember 10, 2012 at 5:33 PMHi Sandra!

Thanks for letting me know. The link got broken somehow; I’ve fixed it now, so you can download the worksheets and place value slide template.

ReginaSeptember 10, 2012 at 6:06 AMThis was very helpful. I am having a very hard time teaching this concept to my fifth grade students. I can’t wait to start this with them! 🙂

Peter PriceSeptember 10, 2012 at 5:34 PMThanks for the comment, Regina. I’m glad this was helpful.

MaryOctober 28, 2012 at 8:52 AMGoing to try this with my co-teaching class this week. Just might help. Thanks.

Peter PriceOctober 28, 2012 at 11:36 AMG’day, Mary! Thanks for the comment, glad you found this useful.

CamilleSeptember 19, 2013 at 8:23 PMThanks Peter!

Your videos are fantastic and very helpful! I spent about an hour fiddling with the place value slide and laminating etc…can’t wait to try it out!

Camille

Peter PriceSeptember 28, 2013 at 9:57 AMThanks, Camille! I’m so glad you like the videos. The place value slide is fiddly to make, but worth it for the benefits of showing so clearly how to multiply by powers of ten.

JoyceSeptember 28, 2013 at 2:50 AMCould you include worksheet or two that includes decimal powers of 10?

For example 95 x .01 or 4.95 x .001

Peter PriceSeptember 28, 2013 at 10:04 AMHi, Joyce, thanks for the comment.

You can subscribe to a 13-week series of free worksheets at http://freemathworksheets.classroomprofessor.com. If you select the 3-5 series, you will receive worksheets at this level. Our “Mental Strategies” eBook contains examples of the sort of question you are looking for. I will also email you privately about this.

Brown Maths TeacherOctober 17, 2013 at 7:20 PM“Telling students to move the decimal point is like asking them to rearrange the letters of the alphabet because it happens to suit the teacher’s strange ideas of alphabetical order.”

My idea of moving EITHER the WHOLE PLACE VALUE DIAGRAM (yes, including the decimal point) OR THE DIGITS WITHIN THE DIAGRAM constitutes a menu of paradigms which students and teachers can use as they see fit. The decimal slide rule resource is just one of many resources which can be deployed to achieve this. I do not in any way advocate changing the order of the alphabet from one lesson to the other. I was taught to move the decimal point and I still have a good understanding of place value. I have taught it successfully to supposedly “failing” students aged 14 or more who had never understood the method of moving the digits. This method for multiplying or dividing by powers of ten then becomes an established fact which can be built upon. To use a simile, basic skills such as these are like an alphabet which students need to know in order to be able write words and sentences. I would much rather kids know a method which works than they are taught for understanding, don´t understand, become disengaged, and therefore can´t move on.

Educationists are always proposing magic bullet, one size fits all strategies such as this. This is normally to further their own career. They don´t work!

Peter PriceNovember 22, 2013 at 9:28 AMThanks for your comment!

My comment about the alphabet was a bit exaggerated to get readers’ attention.

But I do think that telling students to “move the decimal point” is both unhelpful and misleading. Of course it “works”, but in a mindless, nonsensical sort of way. The decimal point is a marker for the boundary between the ones place and the tenths place, between the whole number part and the fractional part. As such, it is incapable of moving. In my view, since this common instruction does not have any meaning in the mathematical domain, we shouldn’t use it.

I cannot budge on the idea of children understanding what they are doing: please, please, please, let all mathematics teachers aim for this. Having a “method that works” is fine, provided a) you know the method and can accurately recall it when you need it, b) you don’t confuse it with other similar methods, and c) you don’t misapply it, thus getting an incorrect result.

Thanks for the comment about magic bullets! I hate this approach also. My entire focus is on understanding the underlying maths, as a way of figuring out methods to solve problems.

LoisNovember 6, 2013 at 11:13 AMI would love to watch the video using the place value slide. It sounds great and I already made a slide. Where to now?

Peter PriceNovember 22, 2013 at 10:09 AMG’day, Lois, thank you for your comment!

I suggest you have a look at this video and set of free worksheets, which are about dividing by 10, 100 or 1000. Place value slides would be an obvious resource to incorporate into this lesson.

http://freemathworksheets.classroomprofessor.com/dividing-by-10-100-1000/

Let me know how you go! I’d love to have some feedback about what you thought, or any questions you might have.