#1**+1 **

We can use similar triangles to find the radius, R, when the height of the sand = 30mm

So we have...

10 /24 = R / 30 multiply both sides by 30

30 * 10 / 24 = 12.5 mm

So the volume of the sand is now = [ (1/3) pi ( 12.5)^2 * 30 ] m^3

And since the sand flows out at 50mm^3 / sec......the time you have to answer the question =

[ (1/3) pi ( 12.5)^2 * 30 ] / 50 ≈ 98 sec

CPhill
May 17, 2017