Question

A car travels at 54 km/has for first 20s, 36 km/has for next 30s and finally 18 km/h for next 10s.find average speed.

Answer 1

distance travelled in first case =54×20×5/18=300m
distance travelled in second case =36×30×5/18 =300m
distance travelled in third case =18×10 ×5/18=50m
average speed =total distance travelled /total time
=300+300+50/20+30+10
=650/60
=10.83 m/s

Answer 2

Hey! ! !

Solution :-

☆ average speed 
are in hours so first changing them in seconds
=>54×5/18=15m/s
=>36×5/18=10m/s
=>18×5/18=5m/s

distance = speed × time
=30×60
=1800metre

average speed=1800/60
=30m/s

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☆ Regards :- ♡♡《 Nitish kr singh 》♡♡