[問題] GWD 0-8

[myron]

A thin piece of wire 40 meters long is cut into two pieces. One piece is used to form a circle with radius r, and the other is used to form a square. No wire is left over. Which of the following represents the total area, in square meters, of the circular and the square regions in terms of r?

(A)pai r^2
(B)pai r^2 + 10
(C)pai r^2 + 1/4 pai^2 r^2
(D)pai r^2 + (40 - 2 pai r)^2
(E)pai r^2 + (10 - 1/2 pai r)^2

ans:(E)
不知道這題該如何解??

[JS]

Area of the Circle - Pai r^2
Circumference Of the Circle 2r*Pai

40-2r*Pai = the length of the left over wire after making the circle

40-2r*Pai/4 = side of the Square

Pai r^2+(10-1/2Pai)^2=total area of the circle and the square

[myron]

JS, thanks.

[Annesft]

喔~少算了剩下的繩子要再除以四才能算面積...
難怪怎麼算都怪怪的...
謝啦!!