two vhiles move in opposite dirctions to each other with constant speeds of 20 m/s and 30 m/s if the initial distance betwen the vehicles is 100 km. how many second later do they meet

The distance between them decreases at a rate 50 m/s.

Time required to meet
t = 100,000 m/50 m/s
= 2000 seconds
= 33 minutes & 20 seconds