document.write( "Question 98870: A student has grades on three test from the MAT 101 course. The grades are 76, 80, and 72. What must he earn on test 4 to have an average of at least 80? \n" ); document.write( "

Algebra.Com's Answer #71990 by doukungfoo(195) $\"\"$ $\"About$

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To find an average for a group of four numbers you must add the numbers together and divide by four. So using the given information we can setup an equation to solve for the final test score which we will call x\r
\n" ); document.write( "\n" ); document.write( " $\"%2876%2B80%2B72%2Bx%29%2F4=80\"$
\n" ); document.write( "First thing to do is add 76 + 80 + 72 together
\n" ); document.write( " $\"%28228%2Bx%29%2F4=80\"$
\n" ); document.write( "Now to futher simplify the equation we need to get rid of the 4 to do that you need to multiply both sides of the equal sign by 4
\n" ); document.write( " $\"%28%28228%2Bx%29%2F4%29%2A4=80%2A4\"$
\n" ); document.write( " $\"228%2Bx=320\"$
\n" ); document.write( "Next solve for x by subtracting 228 from both sides of the equal sign
\n" ); document.write( " $\"228-228%2Bx=320-228\"$
\n" ); document.write( "x= 92
\n" ); document.write( "So we find that the last test grade needs to be at least a 92 to achieve and average of 80
\n" ); document.write( "To check answer just plug in 92 for x in the original equation $\"%2876%2B80%2B72%2Bx%29%2F4=80\"$ \n" ); document.write( "

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