Question

13. 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 [RPET 1996] ; Kerala PMT 2004] (a) 60 km/h (b) 80 km/h (C) 120 km/h (d) 180 km/h​

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