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'.

Q: Problem: a bicycle wheel has a diameter of 0.51 m . how many complete revolutions does it make in 1 km ? 
Options: a ) 246 , b ) 448 , c ) 1408 , d ) 710 , e ) 624

A: e
****
Q: Problem: how many seconds will a train 250 meters long take to cross a platform 200 meters long if the speed of the train is 90 kmph ? 
Options: a ) 18 sec , b ) 15 sec , c ) 21 sec , d ) 16 sec , e ) 20 sec

A: a
****
Q: Problem: two pipes can fill a tank in 18 minutes and 30 minutes . an outlet pipe can empty the tank in 45 minutes . if all the pipes are opened when the tank is empty , then how many minutes will it take to fill the tank ? 
Options: a ) 1 / 15 , b ) 1 / 16 , c ) 1 / 11 , d ) 1 / 10 , e ) 1 / 12

A:
a
****