A train moves fast a telegraph post and a bridge 250 m long in 8 sec and 20 sec respectively. What is the speed of the train?
Choices:
A) 70
B) 39
C) 79
D) 75
E) 71
Let the length of the train be x m and its speed be y m/sec.   Then, x/y = 8 =&gt; x = 8y   (x + 250)/20 = y   y = 20.83   Speed = 20.83 m/sec = 20.83 * 18/5 = 75 km/hr.   Answer:75
<result>D</result>
A train moves fast a telegraph post and a bridge 250 m long in 8 sec and 20 sec respectively. What is the speed of the train?