Question

A car covers the first half of the distance
between the two places at 40 km/h and
another half at 60 km/h. The average speed of
the car is:
(a) 40 km/h
(b) 48 km/h
(c) 50 km/h
(d) 60 km/h​

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