A man covers a distance of 1200 km in 70 days resting 9 hours a day if he rests 10 hours a day and w...........

Explanation:

Distance d = 1200km
let S be the speed
he walks 15 hours a day(i.e 24 - 9)
so totally he walks for 70 x 15 = 1050hrs.
S = 1200/1050 => 120/105 = 24/21 => 8/7kmph
given 1 1/2 of previous speed
so 3/2 * 8/7= 24/14 = 12/7
New speed = 12/7kmph
Now he rests 10 hrs a day that means he walks 14 hrs a day.
time = 840 x 7 /12 => 490 hrs
=> 490/14 = 35 days
So he will take 35 days to cover 840 km.