An object covers half the distance with the speed of 20m/s and other half with the speed of 30m/s . Find average speed?

we know time=distance/speed

First half, time is d/20

second half, time is d/30

total time is (d/20) + (d/30) = d((1/20) + (1/30)) = d((3/60) + (2/60))

total time = d(5/60) = d/12

total distance = 2d

Average velocity = 2d/(d/12) = 24 m/s