Five students took a mathematics test. The average mark was 68. If the marks of four boys were 75, 62, 74, and 63, the mark of the fifth boy was:
a. 66 b. 68 c. 76 d. 56 e. None of these
Let x be the mark of the fifth student.
The definition of "average" is "sum of all marks divided by the number of marks".
This means that if the average is X, we have :
Now you know 4 of the 5 marks and you know the average mark. What equation are you going to solve ?