Question

parts of a train cover half of its journey with the speed 30 km per second and other half with 40 metre per second calculate the average speed during whole journey

Answer 1

HEY DEAR ... ✌

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When journey is travelled in equal distances but different speeds then average speed is shown by-
n/average speed=1/v₁+1/v₂+1/v₃...and so on
where n=no of equal distance intervals.
Here
2/v=1/30+1/40
v=120*2/7=34.2 m/s

HOPE , IT HELPS ... ✌

Answer 2

let the distance be x
so time taken =x/60 in first half and x/80 in 2nd half
total time taken =x/60+x/80=7x/240
average speed =distance /time=x/(7x/240)=240/7=34.285meter/sec answer