A man takes 7.5 hours in walking a certain distance and riding back on horse. If he ride both side on horse he would have saved 3 hours 10 min. How much time does he take on walking both sides?

 10:40 hours

1st Case : Going by walk + riding on horse

Time taken = 7:30 hrs.

2nd Case : Going & coming back on horse

Time       7:30 - 3:10 = 4:20 hrs.

Therefore, one side on horse takes = 2:10 hrs.

And, one side walk takes = 7:30 - 2:10 = 5:20 hrs.

Walking both sides will take = 2 × (5:20) hrs. = 10:40 hrs.