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Using Proportions to Estimate Approximate Latitude

Middle School Teacher Marsha Lodge shares her approach
to estimate approximate latitude with her students.

Marsha Lodge
RHAM Middle School
Hebron, CT
Grades 7+

I use proportions to try to estimate approximate latitude with my students. In order to do this, we set up proportions where the minutes gained each week is the numerator and the distance from the equator is the denominator.

Student working with Atlas
Student looking at Atlas

Then we cross products to estimate the approximate latitude.

For example, we have noticed that our hometown location (Hebron) has gained 19 minutes of photoperiod each week and we are located 33 mm from the equator (using a small desk map).

We set up ratios for each Mystery Class location, using how many minutes they have gained in a week multiplied by our distance from the equator and divided that by 19, (our minutes gained each week -- see diagram below).

Diagram of math equation

Using this approach, we have tried to estimate approximate latitudes for each Mystery Class location.

We'll see at the end of the season if our estimates were correct!

If you have advice to share, please write to Journey North >>

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