Question

if a body moves one third of its Total distance by speed 60 km per hour and rest 2 by 3 distance by 80 km per hour calculate the average speed during the motion

Answer 1

Speed(s)=distance(d)/time(t)

Let us assume the total distance travelled to be 3x.

So the car travels x distance with each speed.

Since, s=d/t,
t=d/s
So the total time taken would be
T=x/40 + x/50 + x/60
Total distance, D=3x

Avg speed = D/T = 3x/( x/40 + x/50 + x/60 )
Cancel x from numerator and denominator and solve for average speed.