let distance from there home to office be 60 km
OLD MAN
here old man takes 30 min to cover 60 km
so in 1 min old man covers 2km
YOUNG MAN
young man takes 20 min to cover 60 km
in one min it covers 3 km
old man step out at 10 am
young man step out 5 minutes late
so from 10 am to 10:05 am old man covers 10 km
now suppoae time at clock is 10: 15 am so now old man covers 30 km and young also covers .30 km
so at this time young man catches the old man hence answer is
10:15 am