A car goes from a town to another B with speed of 40 km/h and returns back to town A with a speed of 60km/h.The average speed of the car during complete journey is - (a) 48 km/h b) 50 km/h

let distance from a to b be xkm

D1 =xkm

S1 =40km/hr

t1 =d/s

= x/40hr

D2 =xkm

S2 =60 km/hr

t2 =d/s

= X/60hr

So, average speed =total distance/total time

= X+X/X/40+X/60

=2x/3x + 2x/120

= 2x*120/5x

= 48 km/hr