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 and b together can do a piece of work in 6 days and a alone can do it in 13 days . in how many days can b alone can do it ? 
Options: a ) 12 days , b ) 15 days , c ) 78 / 7 days , d ) 21 days , e ) 22 / 7 days

Answer: c


Question: Problem: two trains , one from howrah to patna and the other from patna to howrah , start simultaneously . after they meet , the trains reach their destinations after 49 hours and 25 hours respectively . the ratio of their speeds is ? 
Options: a ) 4 : 9 , b ) 5 : 7 , c ) 4 : 5 , d ) 4 : 1 , e ) 4 : 2

Answer: b


Question: Problem: if 5 machines can produce 20 units in 10 hours , how long would it take 20 machines to produce 200 units ? 
Options: a ) 50 hours , b ) 40 hours , c ) 25 hours , d ) 12 hours , e ) 8 hours

Answer:
c