If a man walks 20 km at 5 km/hr he will be late by 40 minutes. If he walks at 8 km per hr. How early from the fixed time will he reach ?

Let the fixed time be T and distance be 20 km. At 5 km/hr: time taken = 20/5 = 4 hours. Since he's 40 minutes late, T = 4 hours - 40 minutes = 3 hours 20 minutes = 200 minutes. At 8 km/hr: time taken = 20/8 = 2.5 hours = 150 minutes. Arrival time = T - 150 = 200 - 150 = 50 minutes early. Therefore he reaches 50 minutes before the fixed time. The key is finding the actual fixed time from the first condition, then comparing with the second travel time.