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If you are working a problem involving averages where the numbers are close together, often a fast way to get to the answer is to compare the individual numbers to the average. The idea is that if you have an average of x and one number is x-3, then there must be a number x+3 to balance things out.
\n" ); document.write( "We can use this method in your example to find the answer very quickly. One of the current five scores is exactly the desired average; and the two scores of 75 and 65 balance each other out. The remaining scores are 72 (2 above the desired average) and 69 (1 below the desired average).
\n" ); document.write( "So the student's \"balance\" going into the 6th test is +1; that means she needs to get a score 1 below the desired average in order to get the exact desired average. So the score she needs to get an average of exactly 70 is 70-1=69.
\n" ); document.write( "More realistically, if she needs to get an average of 70 OR MORE to pass, then she needs to get 69 OR HIGHER on the 6th test. \n" ); document.write( "