In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Problem: a train passes a station platform in 20 sec and a man standing on the platform in 12 sec . if the speed of the train is 72 km / hr . what is the length of the platform ? 
Options: a ) 227 , b ) 140 , c ) 160 , d ) 120 , e ) 171
c

Problem: pipes a and b can fill a tank in 3 and 4 hours . pipe c can empty it in 4 hours . if all pipes are opened together , then the tank will be filled in ? 
Options: a ) 3 hr , b ) 1 / 2 hr , c ) 1 hr , d ) 9 / 7 hr , e ) 5 / 3 hr
a

Problem: two trains are running in opposite directions in the same speed . the length of each train is 120 meter . if they cross each other in 36 seconds , the speed of each train ( in km / hr ) is 
Options: a ) 12 , b ) 36 , c ) 28 , d ) 20 , e ) 24

a