Question

A man travels a distance at a speed of 12km/h and returns at 9km/h. if the total time taken by him is 3 hour 30 minutes
, find the distance he travelled one way.

Answer 1

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For I
Speed = 12 km/hr
Let the distance is x km
Time = Distance/ speed
$= \frac{x}{12}$
For Return
Speed = 9km/hr
Time = Distance/Time
$= \frac{x}{9}$
Now Total time is 3 hr and 30 min
= 3.5 hrs
ATQ
$\frac{x}{12} + \frac{x}{9} = 3.5 \\ \frac{3x + 4x}{36} = 3.5 \\ 7x = 3.5 \times 36 \\ 7x = 126 \\ x = \frac{126}{7} \\ x = 18 \: km$
So Distance= 18 km



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Answer 2

Answer: 18 kms

Step-by-step explanation:

Let the total distance be x.

ATQ speeds a=12kmph, b=9kmph

total time T = 3hr30mins= 3½=7/2

Avg speed = 2ab/(a+b)

= 2*12*9/(12+9)

= 72/7

Speed = distance/ time

72/7 = x/(7/2)

=> Total distance x= 36 kms

Hence distance travelled one way = 36/2 = 18kms