Question

 A cylindrical tank 2 meters in diameter, 3 meters high os full of oil. If the specific gravity of 

oil is 0.9, what is the mass of oil in the tank

Answer 1

$$m_{oil}=\rho_{oil}V_{cylinder},$$ $$m_{oil}=\rho_{w}SG_{oil}\pi r^2h,$$ $$m_{oil}=1000\ \dfrac{kg}{m^3}\cdot0.9\cdot\pi\cdot(1\ m)^2\cdot3\ m=8478\ kg.$$