Two trains are moving at 50 kmph and 70 kmph in opposite directions. Their lengths are 150 m and 100 m respectively. The time they will take to pass each other completely is?  Choose one:
A) 7 1/7 sec
B) 7 7/2 sec
C) 7 1/8 sec
D) 7 1/2 sec
E) 7 3/2 sec
70 + 50= 
<gadget id="calculator">70 + 50</gadget>
<output>120</output>
120 * 5/18= 100/3 mps   7 1/2 sec = 150 + 100= 
<gadget id="calculator">150 + 100</gadget>
<output>250</output>
250 m   T= 250 * 3/100 = 15/2 = 7 1/2 sec   Answer: 7 1/2 sec
<result>D</result>
Two trains are moving at 50 kmph and 70 kmph in opposite directions. Their lengths are 150 m and 100 m respectively. The time they will take to pass each other completely is?