In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Problem: john found that the average of 15 numbers is 40 . if 12 is added to each number then the mean of number is ? 
Options: a ) 52 , b ) 45 , c ) 65 , d ) 78 , e ) 64
a

Problem: a rower whose speed is 2.5 km / hr in still water rows to a certain point upstream and back to the starting point in a river which flows at 0.5 km / hr . what is the rower ' s average speed ( in km / hr ) for the total journey ? 
Options: a ) 2.2 , b ) 2.3 , c ) 2.4 , d ) 2.5 , e ) 2.6
c

Problem: if v is the product of the integers from 1 to 30 , inclusive , what is the greatest integer k for which 3 ^ k is a factor of v ? 
Options: a ) 10 , b ) 12 , c ) 14 , d ) 16 , e ) 18

c