SOLUTION: Suppose Amanda's quiz average is 86, and these are her grades: 84,88,82,90,92,x, where x is unknown. Can you determine the missing grade? If yes, calculate. If not, why not?

Algebra ->  Average -> SOLUTION: Suppose Amanda's quiz average is 86, and these are her grades: 84,88,82,90,92,x, where x is unknown. Can you determine the missing grade? If yes, calculate. If not, why not?      Log On


   

Question 47400: Suppose Amanda's quiz average is 86, and these are her grades: 84,88,82,90,92,x, where x is unknown. Can you determine the missing grade? If yes, calculate. If not, why not?
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
To find the average of a set of numbers (grades), add the numbers and divide by the number of numbers (6 in this case). Amanda's average is 86, so:
84%2B88%2B82%2B90%2B92%2Bx%29%2F6+=+86 simplify and solve for x.
436%2Bx%29%2F6+=+86 Multiply both sides of the equation by 6.
436%2Bx+=+516 Subtract 436 from both sides.
x+=+80
The missing grade is 80.