Question 71

To travel 612 km, Train A takes 9 hours more than Train B. If the speed of the Train A is doubled, it takes 3 hours less than Train B. The speed (in km/h) of Train B is:

Solution

Given Distance = 612 km 

Let the speed of B is x km/hr

So, Time taken by B to cover 612 km = $$\frac{612}{x}hr$$

Time taken by A to cover 612 km = $$\left(\frac{612}{x}+9\right)hr$$ (given) 

Speed of Train A = $$\left(\frac{612}{\frac{612}{x}+9}\ \right)\frac{km}{hr}$$

According to Question, 

$$612=2\times\ \left(\frac{612}{\frac{612}{x}+9}\right)\times\ \left(\frac{612}{x}-3\right)$$

$$\frac{612}{x}+9=2\times\ \left(\frac{612}{x}-3\right)$$

$$\frac{612}{x}=15$$

$$x=\frac{612}{15}=40.8\ \frac{km}{hr}$$
Hence, Option B is correct. 

Video Solution

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