Metric Converstion at a Glance

This activity is designed to give students a quicker way to do conversions other that the traditional fraction approach. Students will learn common metric prefixes, kilo, hecto, deca, deci, centi, and milli. Students can also be introduced into why this method works; that moving a decimal left or right is the same as multiplying by a power of 10, which is what one does when converting using fractions.

The topic on metric conversions is sprinkled throughout middle school science and math classes. I introduce it early in middle school classes and then revisit it several times during the year when doing measurements in class and during labs. Some teachers may find that even high school students need a refresher on such conversions. This is a short lesson, needing perhaps only 10 minutes at the high school level. At the middle school level you could use anywhere from 15 to 40 minutes depending on the math level of your students and whether you want to show the students how to convert using fractions in the same lesson.

The activity is self explanatory as you follow the worksheet. Be sure to do several other examples using the blank table on page 4. I have students take turns doing conversions on a table drawn on the board. Beginning students might need prompting. Ask them: What units are given? Where does the decimal go? Where do you move the decimal to? As the students become more comfortable with the system, ask them why they are moving the decimal that particular number of spaces.

Conversion using fractions is challenging to some students. This method makes converting easy and quick. I have also found that my more advanced students prefer to use this system because they do not have to stop and think things like "how centimeters in a kilometer?" You can cut out the table on page 4, laminate and let the student use it as a bookmark. When conversion is necessary they can use a dry erase marker. After much repetition most students will be able to do the conversion in their heads without the use of the table. I do explain the thought process of why this works initially but I find that I need to repeat it often during the year so that all students comprehend that we are just multiplying and dividing by powers of ten (like what we are doing when we use fractions to convert).

You may find that it is better to teach middle school students only the one dimension method first and save the two and three dimensions for later in the year or high school.

Two common issues have come up:
1. Students must be reminded that the decimal goes on the right side of the column with the number for that column to the left of the decimal
2. Students must be careful to put only one number in each column for one dimension, two for two dimensions, and three for three dimensions.

Your more advance students can readily see that you can add columns to the right and left of the table. For example, they can convert .0045 mm to meters or 587kg to cg. Some students break down at this point and can't do it because they ran out of printed columns. It is interesting to not bring this point up first but to just throw one of these numbers out and see which students can expand the concept to larger or smaller numbers than the columns allow.

Students are very interested in prefixes for larger or smaller numbers (giga, mega, nano, micro) and this can lead to discussions about a wide range of subjects (computer memory, nanotechnology).

Throughout the year I add one or two of these questions on each test or quiz paper. In the beginning of the year I give the student the table to use but toward the end of the year I require that the student draw their own (if even needed by that point).

7.2.3.4.2 and 8.1.3.4.2 using appropriate measurements