Question 763034
Let A = 1st Test
Let B = 2nd Test
Let C = 3rd Test
Let D = 4th Test
Let F = Final
Your equation would be:
{{{(A+B+C+D+4F)/8 = F}}}
The eight comes from the 4 tests plus the final is worth 4 tests.
Plug the given test grades into the equation.
{{{(89+90+86+91+4F)/8 = F}}}
Combine like terms.
{{{(356+4F)/8 = F}}}
Multiply both sides by 8.
{{{356 + 4F = 8F}}}
Subtract 4F from both sides.
{{{356 = 4F}}}
Divide both sides by 4.
{{{highlight(89 = F)}}}
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Now find the score on the final to give the student a 90 for the course.
Our equation will now change a little bit. It will no longer be equal to F, we will set it eqaul to 90.
{{{(A+B+C+D+4F)/8 = 90}}}
Plug in the given test values.
{{{(89+90+86+91+4F)/8 = 90}}}
Combine like terms.
{{{(356+4F)/8 = 90}}}
Multiply both sides by 8.
{{{356 + 4F = 720}}}
Subtract 356 from both sides.
{{{4F = 364}}}
Divide both sides by 4.
{{{highlight_green(F = 91)}}}