A train travels the distance between stations P and Q at a speed of 126 km/h, while in the opposite direction it comes back at 90 km/h. Another train travels the same distance at the average speed of the first train. The time taken by the second train to travel 525 km is:

Let the distance between stations P and Q = d

Time taken by the first train to travel from P to Q = $$\frac{d}{126}$$

Time taken by the first train to travel from Q to P = $$\frac{d}{90}$$

Average speed of the first train = $$=\frac{\text{Total distance}}{\text{Total time}}=\frac{2d}{\frac{d}{126}+\frac{d}{90}}=\frac{2\times126\times90}{126+90}=\frac{2\times126\times90}{216}$$ = 105 km/h

Given, Average speed of the second train is same as that of first train

$$=$$>  Average speed of the second train = 105 km/h

$$\therefore\ $$The time taken by the second train to travel 525 km = $$\frac{525}{105}$$ = 5 hours

Hence, the correct answer is Option C