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 tank can be filled by two pipes a and b in 60 minutes and 40 minutes respectively . how many minutes will it take to fill the tank from empty state if b is used for the first half time and then a and b fill it together for the other half . 
Options: a ) 15 mins , b ) 20 mins , c ) 25 mins , d ) 30 mins , e ) 35 mins
d

Problem: a train takes 10 sec to pass a signal post and covers a distance of 10 km in 15 min . find the length of train ? 
Options: a ) 100.1 m , b ) 223.1 m , c ) 111.1 m , d ) 120.3 m , e ) 133.4 m
c

Problem: 36 men can complete a piece of work in 18 days . in how days will 27 men can complete the work ? 
Options: a ) 18 , b ) 20 , c ) 17 , d ) 24 , e ) 21

d