SOLUTION: In a science course, you must average 89 for an A. Your first three tests were 75, 95, and 91. After the first three tests, you find that you must average 90 or better on your rema

Algebra ->  Average -> SOLUTION: In a science course, you must average 89 for an A. Your first three tests were 75, 95, and 91. After the first three tests, you find that you must average 90 or better on your rema      Log On


   



Question 490167: In a science course, you must average 89 for an A. Your first three tests were 75, 95, and 91. After the first three tests, you find that you must average 90 or better on your remaining tests for an A. How many tests do you hae left?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let n = number of tests left
Whatever n is, the sum of the remaining test scores
will be +90n+ or greater
+89+=+%28+75+%2B+95+%2B+91+%2B+90n+%29+%2F+%28+n+%2B+3+%29+
+89%2A%28+n+%2B+3+%29+=+261+%2B+90n+
+89n+%2B+267+=+261+%2B+90n+
+n+=+267+-+261+
+n+=+6+
There are 6 tests left
check:
+89+=+%28+75+%2B+95+%2B+91+%2B+90%2A6+%29+%2F+%28+6+%2B+3+%29+
+89+=+%28+261+%2B+540+%29+%2F+9+
+89+=+801+%2F+9+
+801+=+801+
OK