vA car takes 5 hours to reach a destination by travelling at the speed of 60 km/hr.

Let x h be the required time taken. Then, we have: 

Clearly, the higher the speed, the lesser will be the the time taken.

So, it is a case of inverse proportion.

Now, $60 \times 5=75 \times x$

$\Rightarrow x=\frac{60 \times 5}{75}$

$\Rightarrow x=4$

Therefore, the car will reach its destination in 4 h if it travels at a speed of 75 km/h.