A cube -shaped oil tank which is 1.5-m long is full of oil . If 500L of oil spills out from the tank, how much oil remains in it?

How can the oil spills of rivers and oceans be cleaned ?

It takes 15 min to completely fill an oil tank. However the oil tank is being used via an outlet in the tank which can empty it in 30 min. If this outlet is open, how much time will it take to fill the tank completely? (A) 20 min (B) 25 min (C ) 30 min (D) 40 min