Question 209752
going into final exam, which will count as two-thirds of the final grade,
 Mike has test scores of 86, 80, 84, and 90.
 What score does Mike need on the final in order to earn a B, which requires an average score of 80? 
What does he need to earn an A?
:
Find the average of his test scores:
{{{(86+80+84+90)/4}}} = 85
:
Let x = final exam score which counts {{{2/3}}} (Test count {{{1/3}}})
:
{{{(2x + 85)/3}}} = 80
2x + 85 = 3(80)
:
2x + 85 = 240
:
2x = 240 - 85
x = {{{155/2}}}
x = 77.5 to have a B
;
"What does he need to earn an A?"
{{{(2x + 85)/3}}} = 90
2x + 85 = 3(90)
:
2x + 85 = 270
:
2x = 270 - 85
x = {{{185/2}}}
x = 92.5 to have an A