TASK DEFINITION: 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: Problem: find the principle on a certain sum of money at 5 % per annum for 3 1 / 5 years if the amount being rs . 580 ? 
Options: a ) rs . 500 , b ) rs . 5100 , c ) rs . 530 , d ) rs . 540 , e ) none of these

SOLUTION: a

PROBLEM: 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

SOLUTION: c

PROBLEM: Problem: what is the average of first 21 multiples of 4 ? 
Options: a ) a ) 44 , b ) b ) 77 , c ) c ) 79 , d ) d ) 81 , e ) e ) 82

SOLUTION:
a