Question

A car moves for half of its time at 80 km/h and for rest half of time at 40 km/h . Total distance covered is 60 km .
What is the average speed of the car ?

Answer 1

let the time taken be 't' hours.
average speed= total distance covered/total time taken
distance covered with 80km/h speed.
80*t/2=d1
40t=d1
distance covered with 40 km/h speed
40*t/2=D2
20t=D2
average speed of car= (40t+ 20t)/t
60km/h is the average speed

Answer 2

distance = 60 km 
total time = total distance / total speed 
80 t + 40 t = 60 
t (120 ) = 60 

t= 0.5 
total time =  2 x 0.5 
                = 1 hr 

= total distance / total time taken 
  = 60 / 1 
  = 60 km/ h