Question

a car covers half of the distance with speed 60 km/h. what should be the speed for rest half of the distances so that average speed becomes 90 km/h ?

Answer 1

Answer:

(1) let x/2 distance cover in time t1 & another x/2 distance cover in time t2

t1 = (x/2)/40

t2 = (x/2)/60

t1+t2 = x/48

average speed = x/(t1+t2) 

                    = x/(x/48)

                    = 48Km/hr

(2) as the above

t1 = x/40

t2 = x/60

t1+t2 = x/24

average speed = 2x/(x/24)

                     =48Km/hr 

(3) s1 = 6*2 

          = 12Km.

s2 = 4*3

     = 12Km.

total distance = s1+s2 = 24km.

average speed = 24/5

                     = 4.8Km/hr