document.write( "Question 1143455: A student must have an average (the Mean) on five tests that is greater than or equal to 80% but less than 90% to receive a final grade of B. Devon's grades on the first four tests were 77%, 63%, 92%, and 78%. What range of grades on the fifth test would give him a B in the course? \n" ); document.write( "

Algebra.Com's Answer #764259 by ikleyn(52800) $\"\"$ $\"About$

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document.write( "You need to solve this inequality\r\n" );
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document.write( "    80 <=  < 90.\r\n" );
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document.write( "I will do it step by step :\r\n" );
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document.write( "    5*80 <= 77 + 63 + 92 + 78 + x  < 5*90\r\n" );
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document.write( "    400  <= 310 + x < 450\r\n" );
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document.write( "    400 - 310 <= x < 450 - 310\r\n" );
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document.write( "    90 <= x < 140.\r\n" );
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document.write( "But the value of x is restricted from the above by 100 automatically (= by the definition (!) ), so the \r\n" );
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document.write( "ANSWER is : the student must get any grade equal or greater than 90.\r\n" );
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\n" ); document.write( "\n" ); document.write( "Another closely related question, which left aside, is \"what is the maximum mean grade the student can reach ?\"\r
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\n" ); document.write( "\n" ); document.write( "The answer is $\"%2877%2B63%2B92%2B78%2B100%29%2F5\"$ = $\"410%2F5\"$ = 92.\r
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