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# In an examination, a student's average marks were 63. If he had obtained 20 more marks in Geography and 2 more marks in history, then his average would have been 65. How many subjects were there in the examination?

[ A ]    12
[ B ]    11
[ C ]    13
[ D ]    14
 Answer : Option B Explanation : Let the number of subjects = x Then, total marks he scored for all subjects = 63x If he had obtained 20 more marks for his Geography and 2 more marks for his history, his average would have been 65 Total marks he would have scored for all subjects = 65x Now we can form the equation as 65x- 63x = additional marks of the student = 20 + 2 = 22 2x= 22 x = $22 \over 2$ = 11