document.write( "Question 1156291: During the first 30 miles of city driving, you average 40 miles per hour. For the remainder of the trip, you drive on a highway at a constant rate of 85 miles per hour. Your average speed for the entire trip is given by \n" );
document.write( "r(x) = (30 + x)/3/4+1/85x\r \n" );
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document.write( "where x is the number of miles you have driven on the highway. \n" );
document.write( "(a) How far will you need to drive on the highway to bring your average speed up to 60 miles per hour? \n" );
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