Hemant travels first 40% of total distance at the speed of 1.25 m/sec and takes rest for 24 minutes. Then he covers remaining distance at the speed of 5/3 m/sec. If he took total 2 hours 40 minutes to complete the journey then find the distance of the journey.

Total time = 2 hr 40 min = 160 min. Rest = 24 min, so travel time = 136 min. First 40% at 1.25 m/s = 75 m/min, remaining 60% at 5/3 m/s = 100 m/min. Let distance be D. Time = 0.4D/75 + 0.6D/100 = 136. Solving: D(0.4/75 + 0.6/100) = 136, D(0.00533 + 0.006) = 136, D(0.01133) = 136, D = 12000 m = 12 km. Option A is calculation error, C from wrong speed conversion, D from subtracting instead of adding.