With an uniform speed, a car covers a distance in 8 hours. had the speed been increased by 4 km/hr, the same distance could have been covered in 7 hr and 30 min. What is the distance covered ?

Let the speed of car be x km/hr
Distance = Speed × Time
Distance = 8x km
According to the question,
$$\eqalign{ & \Rightarrow \left( {x + 4} \right) \times 7.5 = 8x \cr & \Rightarrow 7.5x + 30 = 8x \cr & \Rightarrow 8x - 7.5x = 30 \cr & \Rightarrow 0.5x = 30 \cr & \Rightarrow x = \frac{{30}}{{0.5}} = 60{\text{ km/hr}} \cr} $$
Required distance :
= 8 × 60
= 480 km