A 600 meter long train crosses a signal post in 30 seconds. How long will it take to cross a 3 kilometer long bridge, at the same speed?  Answers:
A) 4 min B) 2 min C) 8 min D) 3 min E) 5 min
S = 600/30= 
<gadget id="calculator">600/30</gadget>
<output>20</output>
20 mps   S= 3600/20= 
<gadget id="calculator">3600/20</gadget>
<output>180</output>
180 sec= 4 min   Answer: 3 min
<result>D</result>
A 600 meter long train crosses a signal post in 30 seconds. How long will it take to cross a 3 kilometer long bridge, at the same speed?