A train covered a distance at a uniform speed .if the train had been 6 km/hr faster it would have been 4 hour less than schedule time and if the train were slower by 6 km/hr it would have been 6 hrs more.find the distance.  Choose one.
A) 720 km B) 820 km C) 920 km D) 620 km E) 780 km
Let t be the usual time taken by the train to cover the distance   Let d be the distance, s be the usual speed   Usual time taken =&gt; d/s = t =&gt; d=ts   d/(s+6) = t-4   ts/(s+6) = t-4   ts = ts+6t-4s-24   6t - 4s - 24 = 0 --&gt; (1)   d/(s-6) = t+6   ts = ts-6t+6s-36   -6t + 6s - 36=0 ---&gt;(2)   Solving (1) nd (2), v get   s = 30 km/h   t = 24 hrs   d = t * s   d = 30 * 24= 
<gadget id="calculator">30 * 24</gadget>
<output>720</output>
720 km   720 kmNSWER:720 km
<result>A</result>
A train covered a distance at a uniform speed .if the train had been 6 km/hr faster it would have been 4 hour less than schedule time and if the train were slower by 6 km/hr it would have been 6 hrs more.find the distance.