A tank of 100 litres is filled with kerosene. Ram replaces 10% of kerosene with water and repeats this procedure 4 times. What is the amount of kerosene left in the tank?
Answer: B
As Ram replaces 10% of kerosene with water, the amount of kerosene left is 90%.
As the replacement is done four times,
After 1st replacement, kerosene left is : 0.9*100 = 90 litres
After 2nd replacement, kerosene left is : 0.9*90 = 81 litres
After 3rd replacement, kerosene left is : 0.9*81 = 72.9 litres
After 4th replacement, kerosene left is : 0.9*72.9 = 65.61 litres