Question 845907
AVG  on tests = (earned points)/(number of points possible).  For 4 tests, the best possible score is 400 points (100 each).  <P>
.83 = x/400 and x = 400*.83 = 332 points.<P>
Call the points you'll receive on the 5th test y.  The total possible points in 5 tests is 500.  (332+y)/500 = .9<P>
332+y = 450<P>
y = 118<P>
You'd need 118 points out of 100 to achieve a 90%.  Unless there's extra credit, you cannot achieve 90%.<P>
The best possible grade you can achieve is 332+100 = 432/500 = .864 - 86.4%