How High is that Similar Triangle?

Duration: 60-90 mins



Grade Levels

Elementary SchoolMiddle School


This lesson teaches students to use similar triangles and congruent angles with “shadow reckoning” to find out the height of a tall object on your school grounds. It is inspired by the maintop on USS Constitution, where some of the crew were stationed 85 to 90 feet above the deck during battle.

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Handouts (PDF Format)

Flagpole WorksheetView / Download
Maintop in Battle IllustrationView / Download
Sailors Aloft IllustrationView / Download