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Suppose the grades on your first four exams were \(78 \%, 92 \%\), \(60 \%,\) and \(85 \%\). What would be the lowest possible average that your last two exams could have so that your grade in the class, based on the average of the six exams, is at least \(82 \%\) ?

Short Answer

Expert verified
The lowest possible average for the last two exams is 88.5%.

Step by step solution

01

- Find the total percentage required

To determine the minimum average needed, start by finding the total percentage required for all six exams to achieve an average of at least 82%. Multiply 82% by 6: \[ Total \text{ required} = 82\text{ \text% \times 6} = 492\text{ \text% } \]
02

- Calculate the total so far

Next, find the total percentage obtained from the first four exams: \[ 78\text{ \text% } + 92\text{\text% } + 60\text{ \text% } + 85\text{ \text% } = 315\text{ \text% } \]
03

- Determine the percentage needed from the last two exams

Subtract the total percentage obtained from the first four exams from the total required: \[ 492\text{ \text% } - 315\text{ \text% } = 177\text{ \text% } \] This is the total percentage needed from the last two exams.
04

- Find the average needed for the last two exams

To find the average, divide the total percentage needed from the last two exams by 2: \[ \text{Average of last two exams} = \frac{177\text{ \text% }}{2} = 88.5\text{ \text% } \]

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Key Concepts

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

exam grade average
Understanding how to calculate exam grade averages is crucial for managing your overall performance. The average grade is obtained by summing the percentage scores of all exams and then dividing this sum by the number of exams. For example, if you have grades of 78%, 92%, 60%, and 85% for four exams, you first add these up: 78% + 92% + 60% + 85% = 315%. Then, to find the average score of these four exams, divide this total by 4: \[ \text{Average} = \frac{315\text{%}}{4} = 78.75\text{%} \]. This average shows your overall performance across these exams.
percentage calculation
Percentage calculations are an important part of many mathematical problems. When we talk about averages and grades, understanding percentage is essential. To determine an overall percentage, or to find out how much more is needed to reach a goal, you typically follow these steps:
  • Multiply the required percentage by the total number of items (or exams, in this case) to get a required total.
  • Add together the percentages you’ve achieved so far.
  • Subtract this total from the required total to find out how much is still needed.
For instance, to achieve an average of 82% across six exams, you need a total of 492%. If you have already scored 315% from four exams, subtracting this from 492% shows you need 177% from the remaining two exams.
final grade requirement
Calculating the final grade requirement is about determining what scores you need on future exams to achieve your desired average. Here’s a step-by-step process: Add up the percentage scores you already have. For example, with grades of 78%, 92%, 60%, and 85%, the total is 315%. Next, calculate the total percentage required for your target average across all exams. If the target is 82%, multiply by the number of exams (82% * 6 = 492%). Subtract your current total from this required total to find out how much more you need to score (492% - 315% = 177%). Finally, divide this by the number of remaining exams to find the average score needed on these exams: \[ \text{Average for remaining exams} = \frac{177\text{%}}{2} = 88.5\text{%} \]. This tells you the minimum average needed on your final exams to meet your target.
mathematical problem solving
Mathematical problem solving often involves breaking down a problem into manageable steps. Here, we’re dealing with the problem of achieving a desired average grade. Approaching it step-by-step can make it more understandable: First, identify what you already know (the grades from previous exams). Next, determine what you need to find (the average grade required on future exams). Use simple arithmetic operations like addition and subtraction to find the total scores involved, and then division to determine the average. Always verify each step to ensure accuracy. By following a structured approach, complex problems can become simpler and more approachable.

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Most popular questions from this chapter

Write a formala to express each of the following sentences: a. The sale price is \(20 \%\) off the original price. Use \(S\) for sale price and \(P\) for original price to express \(S\) as a function of \(P\). b. The time in Paris is 6 hours ahead of New York. Use \(P\) for Paris time and \(N\) for New York time to express \(P\) as a function of \(N\). (Represent your answer in terms of a 12 -hour clock.) How would you adjust your formula if \(\bar{P}\) comes out preater than \(12 ?\) c. For temperatures above \(0^{\circ} \mathrm{F}\) the wind chill effect can be estimated by subtracting two-thirds of the wind speed (in miles per hour) from the outdoor temperature. Use \(C\) for the effective wind chill temperature, \(W\) for wind speed, and \(T\) for the actual outdoor temperature to write an equation expressing \(C\) in terms of \(W\) and \(T\).

Suppose that the price of gasoline is \(\$ 3.09\) per gallon. a. Generate a formula that describes the cost, \(C\), of buying gas as a function of the number of gallons of gasoline, \(G,\) purchased. b. What is the independent variable? The dependent variable? c. Does your formula represent a function? Explain. d. If it is a function, what is the domain? The range? e. Generate a small table of values and a graph.

Sketch a plausible graph for each of the following and label the axes. a. The amount of snow in your backyard each day from December 1 to March 1 b. The temperature during a 24 -hour period in your home town during one day in July. c. The amount of water inside your fishing boat if your boat leaks a little and your fishing partner bails out water every once in a while. d. The total hours of daylight each day of the year. e. The temperature of an ice-cold drink left to stand.

(Graphing program required.) Use technology to graph each function. Then approximate the \(x\) intervals where the function is concave up, and then where it is concave down a. \(f(x)=x^{3}\) b. \(g(x)=x^{3}-4 x\)

Find \(f(3)\), if it exists, for each of the following functions: a. \(f(x)=(x-3)^{2}\) b. \(f(x)=\frac{1}{x}\) c. \(f(x)=\frac{x+1}{x-3}\) d. \(f(x)=\frac{2 x}{x-1}\) Determine the domain for each function.

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