A sport car going at an average speed of 108 km/h takes 15 minutes to complete a lap on a racing track. How much speed (in km/h) should be increased to complete the lap in 9 minutes?

72

Usual speed = 108 km/h

Time = 15 minutes

Distance = Speed × Time

= 108 × \(\frac{15}{60}\) = 27 km

Speed required to cover 27 km in 9 minutes ,

Speed = \(\frac{27× 60 }{9}\) = 180 km/h

Difference in Speed = 180 - 108 = 72 km/h

So , Speed is increased by 72 km/h .