A car can cover a distance of 420 km in 7 h. By how much has the speed to increase to cover the distance in 6 h?

10 km/h

According to Question ,

Speed = \(\frac{Distance}{Time}\)

Speed = \(\frac{420}{7}\) = 60 km/h

Now ,

If we complete the distance in 6 hours then speed should be

Speed =  \(\frac{420}{6}\)

= 70 km/h

Difference in speed = 70 - 60 = 10 km/h

So , Speed should be increased by 10 km/h