A student scored 69 points on his Psychology 101 midterm. If the average of his midterm and final must be between 78 and 90 inclusive for a B, then for what range of scores on the final exam would a student get a B? Both tests have a maximum of 100 points. Hint: Write a compound inequality-with his average between 78 and 90 inclusive.
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To find the range of scores needed on the final exam, we first calculate the total score required for both the lower and upper bounds of the average. For an average of 78: \[(69 + F)/2 \geq 78\] \[69 + F \geq 156\] \[F \geq 87\] For an average of 90: \[(69 + F)/2 \leq 90\] \[69 + F \leq 180\] \[F \leq 111\] Since the final exam can only be a maximum of 100 points, we then limit our upper bound to 100. Thus, the range of final exam scores needed for a B is: \[87 \leq F \leq 100.\] This means the student must score between 87 and 100 points on the final exam for a B!