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: of the final grades received by the students in a certain math course , 1 / 5 are a ' s , 1 / 4 are b ' s , 1 / 2 are c ' s , and the remaining 30 grades are d ' s . what is the number of students in the course ? 
Options: a ) 80 , b ) 110 , c ) 160 , d ) 600 , e ) 400
d

Problem: boys and girls in a class are writing letters . there are twice as many girls as boys in the class , and each girl writes 3 more letters than each boy . if boys write 24 of the 90 total letters written by the class , how many letters does each boy write ? 
Options: a ) 3 , b ) 4 , c ) 6 , d ) 8 , e ) 12
d

Problem: he total marks obtained by a student in physics , chemistry and mathematics is 130 more than the marks obtained by him in physics . what is the average mark obtained by him in chemistry and mathematics ? 
Options: a ) 55 , b ) 65 , c ) 75 , d ) 85 , e ) 95

b