[問題]GWD 18-31

[ilka]

In the figure shown, if the area of the shaded region is 3 times the area of the smaller circular region, then the circumference of the larger circle is how many times the circumference of the smaller circle?

A. 4
B. 3
C. 2
D. 根號3
E. 根號2
答案是 C....
我不太了解題目的原意, 請高手幫忙解答囉.....

[micki]

設 大圓半徑 R 小圓半徑 r "拍" 以p 代替

pR[sup]2[/sup] -pr[sup]2[/sup] = 3pr[sup]2[/sup]
pR[sup]2[/sup]=4pr[sup]2[/sup]

R=2r

所以周長 大圓會是小圓的兩倍

[chris8888]

沒有圖, 請問實際上長怎樣?