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An instructor has graded 19 exam papers submitted by students in a class of 20 students, and the average so far is 70 . (The maximum possible score is \(100 .)\) How high would the score on the last paper have to be to raise the class average by 1 point? By 2 points?

Short Answer

Expert verified
The last student would need to score 90 to increase the average by 1 point and it is not possible to increase the class average by 2 points with the scores limited to 100.

Step by step solution

01

Calculate existing total

Using the formula for the average \( total = average \times number \) calculate the existing total for 19 students. Here, it's \( total_{19} = 70 \times 19 = 1330 \)
02

Calculate required total to increase average by 1

The total required to increase the average by 1 is given by \( total_{20} = (70+1) \times 20 = 1420 \). Reason being, including the score of the last student, the sum of all scores would need to be 1420 for the average to be 71.
03

Find the Score of the Last Student for Average 71

To find out the last student's score, subtract the total for 19 from the total for 20. \( score_{last} = total_{20} - total_{19} = 1420 - 1330 = 90 \)
04

Calculate required total to increase average by 2

The total required to increase the average by 2 is given by \( total_{20} = (70+2) \times 20 = 1440 \)
05

Find the Score of the Last Student for Average 72

To find out the last student's score, subtract the total for 19 from the total for 20. \( score_{last} = total_{20} - total_{19} = 1440 - 1330 = 110 \). But notice that this value exceeds the maximum score possible (which is 100 results in a contradiction hence, it is not possible to increase the class average by 2 points

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Average Calculation
Calculating the average is a fundamental concept in statistics that helps summarize data. The average, or mean, is the sum of all data points divided by the number of points. When looking at scores or grades, this provides a single value representing the overall level of performance.
For instance, if we have a class with 19 students, and their average score is known to be 70, we can calculate the total score for these students by multiplying the average score by the number of students. This is expressed mathematically as:
  • \( \text{Total score} = \text{Average} \times \text{Number of students} \)
In our example, the calculation becomes:
  • \( 1330 = 70 \times 19 \)
This gives us the combined score of the 19 students. Understanding this calculation is crucial for determining changes needed in class assessments or when analyzing academic performance data.
Score Analysis
Analyzing scores involves understanding the needed adjustments to achieve a desired average.
In the exercise, we're tasked with altering the class average by a certain number of points. To increase the class average, we need to consider the total cumulative scores and how much a new score would affect it.
Let's say we want to increase the class average by 1 point. The new desired average becomes 71 for the 20 students. At 20 students, the calculation would be:
  • \( \text{New Total (Target)} = 71 \times 20 = 1420 \)
To find the score of the final exam paper necessary to reach this target, subtract the current total (calculated for 19 students) from this new total:
  • \( \text{Required exam score} = 1420 - 1330 = 90 \)
The correct interpretation of these calculations informs both educators and students of the improvement needed on upcoming assessments.
Class Average
The class average is an important indicator of the overall performance of a group. It can help identify strengths and weaknesses within the class, or even evaluate teaching effectiveness.
In scenarios where one wishes to increase the class average, different strategies might be employed to determine feasible adjustments. If a student wants to elevate their grade contribution sufficiently, understanding the limitations is essential.
For instance, trying to increase the average by 2 points in our exercise is not possible because the required score for the final student exceeds the exam's maximum possible score of 100. This highlights the logical limits of feasible goals:
  • Trying to attain an average of 72 would mean a necessary score of 110.
  • Since scores cannot exceed 100, achieving a 72 average isn't possible under current constraints.
Understanding class average dynamics helps develop realistic strategies for academic improvement and goal setting.

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