The average mark that Sally need on the next two tests to have an average of 80 for all of the tests is 88.
Since the average mark on the first 4 tests Sally took was 76. The total marks will be:
= 76 × 4
= 304
Since she wants an average of 80 on 6 test, the total will be:
= 80 × 6
= 480
Therefore, the average needed in the two tests will be:
= (480 - 304) / 2
= 88
The average is 88.
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