| Purpose: |
To provide practical
application of the concept of ratios, to estimate
heights, and to work on measurement and computation
skills. |
| Season: |
All, depending on weather |
| Materials: |
Meter or yard stick Paper,
Pencil Tape measure (optional) |
| Description: |
Estimating the height of an
unknown object by comparing its shadow to the height of
an object already measured. |
| Procedure: |
- Review concepts of ratio and proportion and then
identify situations where estimating the height
of an object is needed.
- Select a variety of tall objects on the
playground--flag pole, trees, goal posts,
buildings--and have students use the following
steps to estimate their heights:
- 1. Measure the shadow of a tree or other
tall object (see illustration). This may
be done with a tape measure or by pacing.
- 2. Place a yard or meter stick in a
vertical position on the same slope as
the tree and measure the stick's shadow.
The lengths of the two sides of the
triangle formed by the stick and its
shadow, XYZ, are thus known and in
proportion to the sides of the triangle
ABC made by the tree and its shadow.
*Set up a ratio or proportion problem and work it out:
 
|
| Extension: |
Invite a forester to come to
class and discuss the techniques used to estimate the
height of the trees and to determine board feet. |