A train 210 m long passed a pole in 21 sec. How long will it take to pass a platform 310 m long?	Choose the correct answer:
A) 19
B) 32
C) 52
D) 74
E) 83
Speed = 210/21= 
<gadget id="calculator">210/21</gadget>
<output>10</output>
10 m/sec.   Required time= (210 + 310)/10= 
<gadget id="calculator">(210 + 310)/10</gadget>
<output>52</output>
52 sec.   Answer: 52
<result>C</result>
A train 210 m long passed a pole in 21 sec. How long will it take to pass a platform 310 m long?