try to get answer...

Simple explanation:

Difference between travel time is 3 hours. Simply saying, at 10kph, it took 9 hours, and at 15kph, it took him only 6 hours, if he want to arrive at noon, the travel time must be 7 hours, and that is attainable at 12.857 kph speed.

let time to reach the destination be x therefore, at 15kph he took x-1 hrs and at 10kph he took x-1hrs now distance is same so, 15(x-1)=10(x+2) 15x-15=10x+20 5x=35 x=5 distance=10(x+2)=10 9=90km or distance=15(x-1)=15 6=90km now time=x+2=7hrs now subtract 7hrs from 2PM to find the time at when he started so speed=90/7kph

15(t)=d 10(t+3)=d t=6 d=90 speedrequired(t+1)=90 speedrequired=90/7 km/hr...