一道prep6的数学题

且敛风翼 · 发表于 2018-11-25 13:34:05

The volume of a sphere with radius r is given by . A solid sphere of radius r that is made of a certain material weighs 40 pounds. The figure above shows half of a spherical shell made of the same material. What is the weight, in pounds, of the entire spherical shell if the outer radius is 5r and the inner radius is 2r ?

120
360
840
1,080
4,680

spicytaco · 发表于 2018-11-25 14:07:23

如果我没理解错的话，应该是个球体，内部是空心的..小球体
The figure above 的实心体积应该是  4/3*pi*(5r)^3  -  4/3*pi*(2r)^3 也就是大球减去小球
算下来是 4/3*pi*117r^3

已经知道 4/3*pi*r^3 为40磅，那么4/3*pi*117r^3  除以4/3*pi*r^3就得出为117
然后乘以40就是重量，等于4,680

一道prep6的数学题

所属分类: GMAT考试

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