A container contains 120 lit of Diesel. From this container, 12 lit of Diesel was taken out and replaced by kerosene. This process was further repeated for two times. How much diesel is now there in the container?

Step 1: Understand the setup

• Initial quantity of Diesel = 120 liters
• Each time, 12 liters of Diesel is removed and replaced with 12 liters of kerosene
• This process is repeated 3 times in total

Step 2: Use the successive replacement formula

Formula:

Remaining quantity = Initial quantity × (1 - amount removed / total quantity)ⁿ

Here:

• Initial quantity = 120 liters
• Amount removed = 12 liters
• Total quantity = 120 liters
• n = 3 times

Remaining Diesel = 120 × (1 - 12/120)³
                 = 120 × (1 - 0.1)³
                 = 120 × (0.9)³
                 = 120 × 0.729
                 = 87.48 liters

Answer: 87.48 liters

After replacing 12 liters of Diesel with kerosene three times, the container will have 87.48 liters of Diesel left.

This type of problem falls under the category of successive replacement or dilution. It’s commonly found in competitive exams to test understanding of geometric progression and logical reasoning. The method models real-life processes such as repeated mixing or replacement in chemical or fluid operations.