Farida cycles from her home to the mandi at 12 km/h and comes back along the same road at 8 km/h. Had she cycled at 10 km/h each way, the round trip would have taken her 15 minutes less. The distance from her home to the mandi (in km) is:

With d km each way, d/12 + d/8 = 5d/24 hours against 2d/10 = d/5 hours. The saving is 5d/24 − d/5 = d/120 hours = 1/4 hour, so d = 30 km. (Check: 2.5 + 3.75 = 6.25 hours against 6 hours.) 60 km is the round trip, not the one-way distance. Setting the 15 minutes against the difference of the two one-way times, d/8 − d/12 = 1/4, gives 6 km; setting it against the outward leg alone, d/10 − d/12 = 1/4, gives 15 km — the saving is spread across BOTH legs.