A car starts with the speed of 70 km/hr with its speed increasing every two hours by 10 km/hr. In how many hours will it cover 345 kilometers ?

4.5 hrs

We know,

Distance = Speed × Time

Distance covered by car in first 2 hours = 70 × 2 = 140 km

Speed for next 2 hour = ( 70 + 10 ) = 80 km/hr

Distance covered by car in next 2 hours = 80 × 2 = 160 km

New speed for next hours = ( 80 + 10 ) = 90 km/h

Total distance traveled in 4 hours = 140 + 160 = 300 km/h

Remaining distance to be traveled = 345 - 300 = 45 km

Time take by car to cover it = \(\frac{45}{90}\)

= \(\frac{1}{2}\) hour

Total time taken = 4 hour + \(\frac{1}{2}\) hour 

= 4\(\frac{1}{2}\) hours