the complete question in the attached figure
Volume of the sand V=(1/3)*h*π*r²
we have that
h=30 mm
r=10 mm
v=(1/3)*30*π*10²=1000≈3140 mm³
the rate is 50 mm³/seg
50 mm³--------------------------------------> 1 seg
3140 mm³-------------------------------- X
x=3140/50=62.8 seg
the answer is 62.8 seg
