[問題]考古題Form21 sec1 DS-Q11

[凱薩琳]

When a rectangular label, 21.5 centimeters long, is wrapped around the cured surface of a solid circular cylinder with its shoryer ends overlapping, it exactly covers the curved surface. What is the volume of the cylinder in cubic centimerters, if the thickness of the label is ignored?

(1)The label overlap is 0.5 centimeter
(2)The width of the label is 7.5 centimerters

Ans:C

[StanleyHuang]

題目是說有張21.5cm長的標籤要貼在罐頭上，標籤繞了一圈後有一些重疊的地方，不過可以剛好把整個罐子的周圍都蓋住，然後要問說這個罐子的容量是多少...
(1) 重疊的部分是0.5cm ==> 罐子的圓周 = 21 cm = 2*PI*r
(2) 標籤的寬度是7.5cm

罐子的容量 = 底面積*高 = (2*PI*r) * (7.5) = 21*7.5
所以選(C)