s student discovered that his mathematics mark was incorrectly recorded as 39% instead of 93% determine students correct report card average

Question

student has six marks on his report card his overall average is 75% but after looking more closely at his marks student discovered that his mathematics mark was incorrectly recorded as 39% instead of 93% determine students correct report card average

Answer 1

As with many averaging problems, start off with the general form for averaging in mind:  (The sum of all the numbers)/(The number of numbers)

 

There are six test scores averaging 75%; this can be written as  

 

(A + B + C + D + E + F)/6 = 75

 

Multiplying both sides by 6 to simplify leaves us with

 

A + B + C + D + E + F = 450

 

Originally, one of the tests (let's assume test F) was scored at 39. The equation can now be written as

 

A + B + C + D + E + 39 = 450

 

Subtract 39 from both sides to remove the incorrect score

 

A + B + C + D + E = 411

 

Then add 93 to both sides to replace test F

 

A + B + C + D + E + 93 = 504

 

Now you have the sum of all the (correct) scores, so divide by the number of tests, 6, to get the answer.

 

(A + B + C + D + E + 93)/6 = 84

 

The student's average is 84.