Math
Lesson Plan
Converting My Thinking
Learning
Objective:
Estimate
and calculate conversions between measures within the customary and
metric systems.
Teacher
Directions:
When you travel around the world, the metric system is more commonly
used than what is often called the "customary" system (which is sort
of ironic). Although you can use calculators to do precise conversions,
it is also good to be able to mentally convert and estimate back and
forth between the two systems.
Here are some situations you could come across:
A road sign says "Paris 800 km."
You are asked to carry something that weighs 30 kg.
A landmark that you want to climb is 200 m high.
In any of those situations, you would most likely wonder what you are getting yourself into. Will it take me a long time to get to Paris? Can I carry that? Do I want to climb that high? If you had taught yourself how to do quick mental conversions you would be able to come up with answers to your questions.
Here’s one process to try. First, you will need to find out the approximate conversions for units you are more familiar with. To do this, go to the following Web site and find out the following conversions:
1 mile
: ____kilometers
1 pound : ____kilograms
1 foot : ____meters
Next, do some quick mental math.
If 1 mile = x kilometers, that is a 1:x ratio; and x is how many times bigger or smaller than 1? Once you know that you will know what to multiply or divide 800 by to find the number of miles.
If 1 pound = ____ kilograms, that is a 1:x ratio; and x is how many times bigger or smaller than 1? Now you know what to multiply or divide 30 by.
If 1 foot = ____ meters, that is a 1:x ratio; and x is how many times bigger or smaller than 1? Now you know what to multiply or divide 200 by.
Once you’ve done the conversions and the mental math, what was your conclusion? Is 800 km a long way? Is 30 kg a lot to carry? Is 200 m very high?
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