JEE Advanced 2015 Paper 1

A nuclear power plant supplying electrical power to village uses a radioactive material of half life T years as the fuel. the amount of fuel at the beginning is such that the total power requirement of the village is 12.5% of the electrical power available from the plant at that time.If the plant is able to meet the total power needs of the village for a maximum period of n T years ,then the value of n is