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A car travels a distance A to B at a spe...

A car travels a distance A to B at a speed of 40km/h and returns to A at a speed of 30km/h. The avera speed for the whole journey is

A

30.2 km/h

B

32.4 km/h

C

34.3 km/h

D

36.3 km/h

Text Solution

Verified by Experts

The correct Answer is:
C
Let AB=s, time taken to go from A to B,
`t_1 = s/40 h` and time taken to go from B to A, `t=s/30 h`
`:. " total time taken " =t_1+t_2 = s/40 + s/30 = (7s)/(120 )h`
Total distance travelled `=s+s=2s :. "Average speed " = ((2s)/(7s))/(120) = 240/7 = 34.3 km//h`
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