document.write( "Question 514009: you have the following grades on your biology test 88, 85, 91 and 92. you have one more test to take and you want to get a final average of 90 on your test. what do you need to get on your final test in order to have an average of 90? \n" ); document.write( "

Algebra.Com's Answer #343248 by drcole(72) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let x be the grade on the last test. The average of the five test grades is therefore:\r
\n" ); document.write( "\n" ); document.write( " $\"+%2888+%2B+85+%2B+91+%2B+92+%2B+x%29%2F5+\"$ \r
\n" ); document.write( "\n" ); document.write( "We want this average to be 90, so we set it equal to 90 and solve for x:\r
\n" ); document.write( "\n" ); document.write( " $\"+%2888+%2B+85+%2B+91+%2B+92+%2B+x%29%2F5+=+90+\"$
\n" ); document.write( " $\"+%28356+%2B+x%29%2F5+=+90+\"$ (combine like terms)
\n" ); document.write( " $\"+356+%2B+x+=+450+\"$ (multiply both sides by 5)
\n" ); document.write( " $\"+x+=+94+\"$ (subtract 356 from both sides)\r
\n" ); document.write( "\n" ); document.write( "So you need a 94 on the last exam to get a 90 average on all five exams. Make sure to check that the average of the five exams is indeed 90! \n" ); document.write( "

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