Three cities, A, B, and C are located such that they form the vertices of an equilateral triangle if joined by straight lines. Rashid travels from A to B at the speed of 40 km/h, from B to C at the speed of 60 km/h and from C to A at the speed of 72 km/h. Find the average speed of Rashid for the entire journey.

54 km/h

According to question ,

AB = BC = CA

LCM of ( 40 , 60 , 72 ) = 360

Let Distance = 360 km

Total distance = 360 + 360 + 360 = 1080 km

Time AB = \(\frac{360}{40}\) = 9 hours

Time BC = \(\frac{360}{60}\) = 6 hours

Time CA = \(\frac{360}{72}\) = 5 hours

Average speed = \(\frac{Total \; Distance }{Total \; Time }\)

= \(\frac{1080}{20}\)

= 54 km/h