A batsman played seven games and scored an average of 80 runs per game. If, in his first five games, he scored 75, 69, 81, 90, and 73 runs, what was the average (arithmetic mean) number of runs scored over the last two games?
Choose the correct choice from the following answers.
A) 65  B) 81  C) 82  D) 86  E) Cannot be determined from the information given.
The first thing to recognize is that to find the average, you take the sum and divide by the number of inputs (games, in this case) you have. Here were have 7 inputs, or games. Therefore, I approach this problem by first writing the following:   (A+B+C+D+E+F+G)/7 = 80   Plug in the sum of the first 5 games (388) for (A+B+C+D+E)   [(388+F+G)/7]= 80   Multiply both sides by 7   388+F+G = 560   Subtract 388 on both sides   F+G = 172   Since the answer asks for the average of the last two games, F and G, all you need to do is take 172 and divide it by 2, giving 86.   The answer is 86.
<result>D</result>
A batsman played seven games and scored an average of 80 runs per game. If, in his first five games, he scored 75, 69, 81, 90, and 73 runs, what was the average (arithmetic mean) number of runs scored over the last two games?