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'.
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Question: Problem: a , b , k start from the same place and travel in the same direction at speeds of 30 km / hr , 40 km / hr , 80 km / hr respectively . b starts two hours after a . if b and k overtake a at the same instant , how many hours after a did k start ? 
Options: a ) 2 , b ) 3 , c ) 4 , d ) 5 , e ) 6

Answer: d


Question: Problem: a can finish a piece of work in 12 days . b can do it in 20 days . they work together for 9 days and then a goes away . in how many days will b finish the work ? 
Options: a ) 6 days , b ) 4 days , c ) 5 days , d ) 3 days , e ) 7 days

Answer: c


Question: Problem: a train consists of 12 boggies , each boggy 15 metres long . the train crosses a telegraph post in 18 seconds . due to some problem , one boggies were detached . the train now crosses a telegraph post in 
Options: a ) 16.5 sec , b ) 12 sec , c ) 15 sec , d ) 20 sec , e ) none of these

Answer:
a