The maximum value of a voltage is 25 volts and it is attained in 24 milliseconds in case of an inductor. At what time does current reach its maximum value?

30 msec

Phase difference between current and voltage is 90º or one fourth of time perod.

Current reaches its maximum value later than the voltage by one-fourth of a period. 

1/4(24 msec) = 6 msec

The current reaches the maximum value at : T = 24 msec + 6 msec = 30 msec