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Learning by Doing

Objective: To understand the concept of finding the value of an algebraic expression.
Materials Required: A-4 sheet, a geometry box
Procedure:
• Take an A-4 sheet and draw few circles by using a
pair of compasses of any measures.

• Measure their radii by using a ruler and note down
in the table as shown below.
• Find the circumferences of the circles you drawn
by substituting the values of radii you measured of
the respective circle.
• As the circumference of a circle is given by the
22
algebraic expression 2p × r units, where p = and r is the radius of the circle.
7

Circle Radius of the circle, Circumference of the circle (2p × r units),
r (in cm) 22
where p = and r is the radius of the circle
7
Circle 1 r = 7 cm 22
2 × × 7 cm = 44 cm
7

Circle 2

Circle 3

127 Introduction to Algebra