A thief stole jewellery from a shop at 8:15 p.m. and left on a bike at a speed of 60 km/h. The police were informed at 8:30 p.m. If the police want to arrest the thief at 9:00 p.m., what should be the minimum speed of the police jeep?

90 km/h

Thief run at 8:15 pm .

Policeman get informed at 8:30 pm . So distance traveled by thief in 15 minutes = \(\frac{60}{4}\) = 15 km

Let speed of policeman = x

Relative speed = x - 60

Time taken by policeman to caught the thief = 30 min

\(\frac{15}{x - 60}\) = \(\frac{1}{2}\)

30 = x - 60

x = 90 km/h

So , speed of policeman should by 90 km/h to caught thief at 9:00 pm.