Velocity of Car = 18 ms^-1

To express this velocity in kmhr^-1 we need the conversion factor which is calculated as under:

1 km = 1000 m

So, 1 m = km

Now, 1 hr = 60 minutes = 60 × 60 s = 3600 s

So, 1 s = hr

Now, Velocity of car = 18

= 18

= kmh^-1

= 64.8 kmh^-1