There are 5 exams in a semester. You have scored 77, 90, 85, and 100 on the previous four exams. What must you make on the fifth exam to get an average of exactly 86 for the marking period?

The correct answer for this question is 78.

Step-by-step explanation:

The average or mean of any variable or mathematical phenomenon is calculated as the division of the sum of all the numbers or items within the particular variable by the total number of items or numbers within the variable.In this case, the marks of the 4 exams in the semester are 77,90,85 and 100 respectively.There are total 5 exams in the semester.Let's suppose that the marks for the 5th exam is x.Therefore, based on the mathematical formula to compute average or mean,to get an overall average of 86 including all the 5 exams, one has to get:-

   

 

 

 

Hence, based on the above calculations,one has has to get 78 on the 5th exam to obtain an overall average of exactly 86.