### 10/10 and the Metric Week

Today is 10th of October or 10/10. As we know, the metric system is based on number 10. Thus, the week ending today has been designated as the metric week..

The National Council of Teachers of Mathematics (NCTM) started the National Metric Week tradition in 1976. Please read a little bit more about the history of the Metric Week here.

You could celebrate the Metric Week doing some metric units puzzles and quizzes. Here's a link to postal stamps and cards celebrating the metric system.

NCTM has tons of related resources so I'll mainly point you there.

I grew up using the metric system, and so I've actually had to learn the imperial system while authoring math materials. These days, it seems, I know the U.S. system better than the people around me... But the metric is sure easier, as far as calculations and conversions go, since you just have to remember it goes by 10s.

In fact, to fully operate in this world, it seems it's best to know both.

Converting between metric and U.S. measuring systems

Here are a few helpful guidelines if you find yourself having to switch between one or the other. I have these conversion factors memorized from much of use. Not that everyone else would actually use these all as much as I do, being in the business of authoring math materials, but anyway:

1 quart ≈ 1 liter, but 1 quart is slightly less.

1 liquid ounce ≈ 30 ml. From this, one can figure out that 1 cup ≈ 240 ml and 4 C ≈ 960 ml.

1 inch = 2.54 cm

It's an awkward number but I need to use this conversion factor constantly, when working with images on my computer, which has a resolution of 96 pixels per inch... but I need the image to print out as 5 cm long or whatever.

You could use 1 inch ≈ 2.5 cm.

Another way is to think about those typical student rulers which are 12 inches = 30 cm. So... 4 inches is 10 cm.

Also... 1 inch might very well be the length of your thumb's last bone (the bone that contains the nail). Check! And 1 cm might very well be the width of any of the other fingernails. Check!

1 yard ≈ 1 meter; better yet 1 yard ≈ 90 cm and 1 meter = 100 cm. You see, that student ruler was 12 inches = 1 foot ≈ 30 cm.

1 mile ≈ 1.6 km. Or, 5,000 meters or 5 K is a popular running distance... about 3 miles.

1 pound is about 450 g, but actually it's easier to remember 1 kg = 2.2 lb.

It's fairly easy to multiply by 2.2. I have a metric scale; I might weigh about 55 kg. 55 x 2 = 110 and 55 x 0.2 = 11. So I weigh about 121 lb.

And 1 ounce ≈ 30 g. Just like 1 liquid ounce was about 30 ml.

To convert anything, go to Google and type

25 lb to kg

8 m to inches

22 km to miles

etc.