Weighted Average Practice Problems & Solutions - Step by Step

Master weighted average calculations with practice problems covering grade averages, speed calculations, and real-world applications. Get step-by-step solutions and tips.

📚Master Weighted Average Calculations with These Practice Problems
  • Calculate weighted averages for academic grades with different exam weights
  • Solve weighted average problems involving speed and distance calculations
  • Apply weighted average formulas to real-world scenarios like building floors
  • Convert percentages to decimals for weighted average calculations
  • Set up equations to find unknown values in weighted average problems
  • Distinguish between regular averages and weighted averages in word problems

Understanding Weighted Average

Complete explanation with examples

Weighted Average: What Does It Really Mean?

A weighted average is an average among numbers with different weights.
Each number has its own weight and, therefore, will affect the weighted average.
Try replacing the word weight with the word importance and in this way its meaning will be better understood.
The numbers are of different importance. One number is more important and another number is less important. It does not mean a large or small number, but simply important.
When a number is more important, it has a greater weight and will have a greater effect on the weighted average.

A - Weighted average formula

A1 - weighted average

Detailed explanation

Practice Weighted Average

Test your knowledge with 7 quizzes

Ivan rolls a dice and records the results:

\( 4,3,1,6,5,3,1 \)

What is the average number resulting from the dice rolls?

Examples with solutions for Weighted Average

Step-by-step solutions included
Exercise #1

What is Monica's average grade if she gets 98 on an assignment that represents 30% and a 95 on an exam that represents 70%?

Step-by-Step Solution

Let's solve the problem by applying the steps we outlined:

  • Step 1: Identify the grade and weight for each component:
      - Assignment: Grade = 98, Weight = 30% (or 0.30)
      - Exam: Grade = 95, Weight = 70% (or 0.70)
  • Step 2: Apply the weighted average formula:
      - Compute the weighted grade for each component:
        Weighted grade for assignment = 98×0.30=29.4 98 \times 0.30 = 29.4
        Weighted grade for exam = 95×0.70=66.5 95 \times 0.70 = 66.5
  • Step 3: Sum the weighted grades to find Monica's average grade:
      - Total weighted average = 29.4+66.5=95.9 29.4 + 66.5 = 95.9

Therefore, Monica's average grade is 95.9 95.9 .

Answer:

95.9 95.9

Video Solution
Exercise #2

What is the average grade of the student who got the following:

GradeWeight40%20%15%25%68739491

Step-by-Step Solution

To find the weighted average grade, follow these steps:

  • Step 1: Convert the percentage weights into decimal form:
    • 40% to 0.40
    • 20% to 0.20
    • 15% to 0.15
    • 25% to 0.25
  • Step 2: Calculate the contribution of each grade by multiplying it by its weight:
    • Grade 68 with weight 0.40: 68×0.40=27.2 68 \times 0.40 = 27.2
    • Grade 73 with weight 0.20: 73×0.20=14.6 73 \times 0.20 = 14.6
    • Grade 94 with weight 0.15: 94×0.15=14.1 94 \times 0.15 = 14.1
    • Grade 91 with weight 0.25: 91×0.25=22.75 91 \times 0.25 = 22.75
  • Step 3: Sum the contributions:
  • 27.2+14.6+14.1+22.75=78.65 27.2 + 14.6 + 14.1 + 22.75 = 78.65

Since the weights sum up to 100%, the weighted average grade is directly this sum.

Therefore, the student's weighted average grade is 78.65 78.65 .

Answer:

78.65 78.65

Video Solution
Exercise #3

What is Michael's score if he gets 79 on the first exam and 83 on the second, given that the weight of the first test is 30% and that of the second is 70%?

Step-by-Step Solution

To solve the weighted average, we will use the following formula:

exam 2 * weight of evaluation 2 + exam 1 * weight of the evaluation 1 = Weighted average

 

We will place the data in the formula, where the weights will be in decimal numbers:

0.3*79 + 0.7*83 = 
23.7+58.1 = 

81.8

 

Answer:

81.8 81.8

Exercise #4

A hotel's overall rating is determined according to a weighted average of several categories. Each category is given a rating and a weighted factor. Below are the ratings for the "Happy Tourist" hotel:

SatisfactionCleanlinessServiceBreakfastRatingWeight50%30%10%10%4.5453

Determine the hotel's overall rating?

Step-by-Step Solution

In order to determine the hotel rating, we must calculate an average.

Below is the weighted average formula:

(value A X weight percentage A)+(value B X weight percentage B)...

First, let's add up all the percentages:

50%+30%+10%+10%=100% 50\%+30\%+10\%+10\%=100\%

Now we must multiply each factor by its weight percentage, convert the percentages to decimal numbers, and add them as follows:

4.5×0.5+4×0.3+5×0.1+3×0.1= 4.5\times0.5+4\times0.3+5\times0.1+3\times0.1=

We then proceed to solve the multiplication exercises:

2.25+1.2+0.5+0.3= 2.25+1.2+0.5+0.3=

Finally we add them up and obtain the following: 4.25 which is the hotel's overall rating.

Answer:

4.25

Video Solution
Exercise #5

A teacher wants to calculate Gabriel's final weighted average.

The following are Gabriel's exam results:

TestExamTestProjectGradeWeight30%15%35%20%84738792

What is Gabriel's final average?

Step-by-Step Solution

To calculate Gabriel's final weighted average, we'll use the formula for a weighted average:

Weighted Average=(Test 1 Grade×Weight 1)+(Exam Grade×Weight 2)+(Test 2 Grade×Weight 3)+(Project Grade×Weight 4) \text{Weighted Average} = (\text{Test 1 Grade} \times \text{Weight 1}) + (\text{Exam Grade} \times \text{Weight 2}) + (\text{Test 2 Grade} \times \text{Weight 3}) + (\text{Project Grade} \times \text{Weight 4})

Next, calculate the contribution of each component:

  • Test 1 Contribution: 84×0.30=25.284 \times 0.30 = 25.2
  • Exam Contribution: 73×0.15=10.9573 \times 0.15 = 10.95
  • Test 2 Contribution: 87×0.35=30.4587 \times 0.35 = 30.45
  • Project Contribution: 92×0.20=18.492 \times 0.20 = 18.4

Now, add all these contributions to find the final weighted average:

Weighted Average=25.2+10.95+30.45+18.4=85 \text{Weighted Average} = 25.2 + 10.95 + 30.45 + 18.4 = 85

Therefore, Gabriel's final weighted average is 85\boxed{85}.

Answer:

85 85

Video Solution

Frequently Asked Questions

What is the difference between a regular average and a weighted average?

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A regular average treats all numbers equally, while a weighted average gives different importance (weights) to different numbers. For example, if exam scores count more than homework scores in your final grade, you need a weighted average where the exam has a higher weight percentage.

How do I calculate weighted average for school grades?

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First, convert percentages to decimals (20% = 0.2). Then multiply each grade by its weight and add them together. For example: (75 × 0.1) + (95 × 0.1) + (85 × 0.8) = 85. The sum of all weights must equal 1.0 or 100%.

What are the steps to solve weighted average word problems?

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1. Read the problem twice to identify what you're solving for 2. List all values and their corresponding weights 3. Set up the weighted average formula 4. Solve the equation algebraically 5. Check that your answer makes sense in context

How do I find a missing value in a weighted average problem?

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Set up the weighted average equation with the unknown as a variable (like X). Use the formula: weighted average = (sum of all weighted values) ÷ (sum of all weights). Then solve the resulting equation algebraically to find the missing value.

Can weighted averages be used for non-academic problems?

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Yes! Weighted averages apply to many real-world situations including calculating average travel speed over different portions of a journey, determining average building heights in neighborhoods, or finding average prices when quantities vary.

What common mistakes should I avoid in weighted average calculations?

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Common mistakes include: forgetting to convert percentages to decimals, not matching each value with its correct weight, rushing without reading what the question actually asks for, and confusing weighted average problems with regular average problems.

How do I check if my weighted average answer is correct?

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Verify that: 1) All weights sum to 1.0 (or 100%), 2) Your answer falls within the range of the given values, 3) The answer is closer to values with higher weights, 4) Substituting back into the original equation gives the stated weighted average.

When do I use weighted averages instead of regular averages?

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Use weighted averages when different data points have different levels of importance or when they represent different quantities. Examples include calculating final grades (exams vs. homework), average speed over different distances, or average values when sample sizes vary.

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