check a website called math-way without the dash it might help
length of pipe= 30m
Inside dia. = 1.2m
Outside dia. = 1.8m
Volume of concrete= (outside dia. - inside dia.)h
V= (pi)
v= [(3.14*0.9*0.9)-(3.14*0.6*0.6)]30
v= (3.3534-1.1304)30
v=(2.233)30 = 66.690m cube
since it's volume the answer 66.690 is in cubic meters.
n>-6 and n<3 (there's your answer my friend)
