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 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
c

Problem: i flew my tiny seaplane to visit my mother . on the flight up , i flew at 110 mph . on the way home , i flew 90 mph . what was my average speed for the trip ?
Options: a ) 198 mph , b ) 110 mph , c ) 88 mph , d ) 100 mph , e ) 99 mph
d

Problem: two boys started running simultaneously around a circular track of length 4800 m from the same point at speeds of 60 km / hr and 100 km / hr . when will they meet for the first time any where on the track if they are moving in opposite directions ?
Options: a ) 105 , b ) 106 , c ) 107 , d ) 108 , e ) 109
d