How to write the fifth question on page 42 of the math exercise book: the area of the shaded part on the right is 40 square centimeters. How much is the area of a big circle larger than that of a small circle? Assuming that the radius of the big circle is R and the radius of the small circle is R, according to the meaning of the question, the shadow area = the area of the big triangle line-the area of the small triangle, that is:

R square ÷2-r square ÷2=40

Square of R-Square of R = 40× 2 = 80.

Great circle region-small circle region

=π×R square -π×r square

=π×(R square -r square)

=3. 14×80

=25 1.2 (cm2)

A: The area of the big circle is 25 1.2 cm 2 larger than that of the small circle.

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