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: if two of the 4 expressions x + y , x + 5 y , x - y , and 5 x - y are chosen at random , what is the probability w that their product will be of the form of x ^ 2 - ( by ) ^ 2 , where b is an integer ? 
Options: a ) 1 / 2 , b ) 1 / 3 , c ) 1 / 4 , d ) 1 / 5 , e ) w = 1 / 6
e

Problem: the element being searched for is not found in an array of 100 elements . what is the average number of comparisons needed in a sequential search to determine that the element is not there , if the elements are completely unordered ? 
Options: a ) 25 , b ) 50 , c ) 75 , d ) 100 , e ) 125
d

Problem: the difference between a number and its three - fifth is 50 . what is the number ? 
Options: a ) 185 , b ) 190 , c ) 160 , d ) 120 , e ) 125

e