请教OG12 数学题 197 200

lucy1006

请教大家二题OG12的数学题

197. A point on the edge of a fan blade is rotating in a plane is 10 centermeters from the center of the fan. What is the distance traveled , in centermeters, by this point in 15 seconds when the fan runs at the rate of 300 revolutions per minutes?!

          A.750π

          B1500π

          C.1875π

          D.3000π

          E.7500π

答案是B请问有牛牛可以帮忙解释吗？！谢谢

 

200.    of the 50 researchers in a workgroup, 40 percent will be assigned to Team A and the remaining 60 percent to Team B. However, 70 percent of the reserchers prefer Team A and 30 percent prefer Team B. What is the lowest possible number of researchers who will NOT be assigned to the Team they prefer?

         A.15

         B17

         C.20

         D.25

         E.30

答案是A 请教各位 为什么选A吗？！谢谢

[此贴子已经被作者于2009/10/2 9:45:03编辑过]

yaoyao880529

197. 其实就是考你圆的周长，题目是说一个螺旋桨上，有一个点距离圆心10厘米，当这个螺旋桨以300转/分钟的速度转15秒，这个点走过了多少厘米。

转一圈点走过的距离就是周长S=2*pi*10=62.8, 转过的圈数等于（300/60）×15＝75

最后的答案就是62.8×75＝4710

198.先把喜欢B的安排到B，喜欢A的安排到A，多出的30％喜欢A的人分配到B就可以了，答案就是30％×50＝ 15

你下次贴的时候可以把答案一起发上来哈

lucy1006

补上答案了哦 谢谢~

[此贴子已经被作者于2009/10/2 9:45:56编辑过]