Question

Grain is falling from a chute onto the ground, forming a conical pile whose diameter is always three times its height. how high is the pile (to the nearest hundredth of a foot) when it contains 1110 ft3 of grain?

Answer 1

Given that grain is falling from a chute onto the ground, forming a conical pile whose diameter is always three times its height.

So if D is the diameter and h is the height of the conical pile then we can write:

D=3h

We know that diameter = 2r, where r is the radius

2r=3h

$r=\frac{3h}{2}$

Volume of conical pile is given by formula

$V=\frac{1}{3}\pi r^2h$

Given that volume is 1110 cubic feet.

Now plug the values of Volume and r into equation of volume

$1110=\frac{1}{3}\pi (\frac{3h}{2})^2h$

$1110=\frac{1}{3}\pi\cdot\frac{9h^2}{4}\cdot h$

$1110=\pi\cdot\frac{3h^3}{4}$

$1110\cdot\frac{4}{3\pi}=h^3$

$471.098631552=h^3$

take cube root of both sides

7.78103342467=h

Hence height is approx 7.78 feet.