He scored an average of 18 points per game, and the scores of three of these games were {25, 16, 19}. Thus, using the formula for average value,
25+16 + 19 + a + b
--------------------------- = 18, or 25+16+19+a+b = 90
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Now you must go through the list of possible pairs of scores, checking whether the 2 scores given, along with 25, 16 and 19, produce an average score of 18:
First possible pair of scores: {20,22}
Does:
25+16+19 +20+22
------------------------------- = 18 ??
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104
Does --------- = 18? NO. So eliminate the first answer pair {20,22}.
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Move on to the next answer pair {18,18). Is the average score 18?
And so on.
A slightly easier approach would be to combine the 2 scores in each possible answer pair:
25+16+19+36
Does ----------------------- = 18? (that 36 is the sum of 18 and 18).
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