Correct Answer - Option 2 : 100/11 km/hr
Given:
A person covers 25% of the distance at the speed of 5 km/hr
He covers 1/3rd of the remaining at the speed of 25 km/hr
He covers remaining distance at the speed of 10 km/hr
Formula:
Average speed = Total distance/Total time
Calculation:
Let total distance be 100 km
25% of the distance = 100 × (25/100) = 25 km
Remaining distance = 100 - 25 = 75 km
1/3rd of the 75 = 25 km
Remaining distance = 100 - 25 - 25 = 50 km
Time taken by person to cover 25 km distance at the speed of 5 km/hr = 25/5 = 5 hrs
Time taken by person to cover 25 km distance at the speed of 25 km/hr = 25/25 = 1 hr
Time taken by person to cover 50 km distance at the speed of 10 km/hr = 50/10 = 5 hrs
Total time = 5 + 1 + 5 = 11 hrs
∴ Average speed = 100/11 km/hr