A man walked at a speed of 4 km/hr from point A to B and came back from point B to A at the speed of 6 km/hr. What would be the ratio between the time taken by man in walking from point A to B to point B to A respectively?

Time from A to B at 4 km/h: t1 = d/4. Time from B to A at 6 km/h: t2 = d/6. The ratio t1:t2 = (d/4):(d/6) = (1/4):(1/6) = 6:24 = 1:4. Alternatively, the speed ratio is 4:6 = 2:3, so the time ratio (inverse of speed) is 3:2 = 1.5:1. Neither 1:4 nor 3:2 match any of A-D, so 'None of these' (option E) is correct. The key insight is that time is inversely proportional to speed for the same distance.