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Grade 5, Mathematics Volume II, Jiangsu Education Edition.
Measure the diameter of the white semicircle divided by 2, which is the radius of the white semicircle, and then calculate its area S = π r 2/2.

Then measure the radius of the blue semicircle and calculate its area? S=πR^2/2

The area of the drawing part is the difference between the two areas.

Measure the length and width of a rectangle, and then you can calculate its area? S=ab

A rectangle is the diameter of a semicircle. Divided by 2, it is the radius of the semicircle, and its area can be calculated. S=πr^2/2

The area of the drawing part is the sum of the two areas.

You can calculate the area of a semicircle by measuring its radius? S=πr^2/2

The radius of the semicircle is the height of the white triangle, and the area of the white triangle is S=2a*a/2.

The area of the drawing part is the difference between the two areas.