Lesson Study Video for Area of the Circle: Kudo's Solution (6 of 7)

Start 37:05, length 5 min. 16 secs.

The teacher asks students to create a triangle using the sectors of a circle and to find its area. At 30:14 he asks four students to put up their figures. The first is Miss Kamoda who puts up a different parallelogram with two rows of sectors one above the other. 

The teacher gives students three minutes to derive a formula for this new parallelogram. Only a few students finish so he asks the other students to go see and discuss the other students’ solutions.

At 00:37:00, a student (Kudo) explains his solution. He measured the diameter as 20 cms and used a square to represent the circumference to get the formula 20 x square ÷ 4, which he writes as 5 x square.

In the ensuing discussion, Yoshizawa explains how to change this formula into (diameter)÷4x(circumference) enabling the teacher to relate the two formulas.

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