Calculating Average Marks After Adding Grace Marks

The problem asks us to find the average marks of 5 students after adding 5 grace marks to each student's original score. We are given the initial marks obtained by the 5 students.

Understanding the Problem

We are given the initial marks of 5 students:

• Student 1: 21
• Student 2: 27
• Student 3: 19
• Student 4: 26
• Student 5: 32

5 grace marks are added to each student's mark. This means we need to increase each score by 5 and then calculate the average of these new scores.

Step-by-Step Calculation of Revised Marks

First, let's find the revised marks for each student by adding 5 to their original marks:

• Student 1 revised marks: \(21 + 5 = 26\)
• Student 2 revised marks: \(27 + 5 = 32\)
• Student 3 revised marks: \(19 + 5 = 24\)
• Student 4 revised marks: \(26 + 5 = 31\)
• Student 5 revised marks: \(32 + 5 = 37\)

So, the revised marks for the 5 students are 26, 32, 24, 31, and 37.

Calculating the Sum of Revised Marks

To find the average of the revised marks, we first need to find their sum.

\text{Sum of revised marks} = 26 + 32 + 24 + 31 + 37

Let's add these numbers:

\text{Sum} = 58 + 24 + 31 + 37

\text{Sum} = 82 + 31 + 37

\text{Sum} = 113 + 37

\text{Sum} = 150

The sum of the revised marks is 150.

Calculating the Average of Revised Marks

The average is calculated by dividing the sum of the marks by the number of students.

\text{Average} = \frac{\text{Sum of revised marks}}{\text{Number of students}}

Number of students = 5

\text{Average} = \frac{150}{5}

\text{Average} = 30

The average marks of the revised marks of the students is 30.

Alternative Method: Using Properties of Average

There is a useful property of averages: if every value in a dataset is increased by a constant value, the average of the dataset also increases by the same constant value.

Let's calculate the initial average marks first.

Sum of initial marks = \(21 + 27 + 19 + 26 + 32\)

\text{Sum} = \(48 + 19 + 26 + 32\)

\text{Sum} = \(67 + 26 + 32\)

\text{Sum} = \(93 + 32\)

\text{Sum} = 125

Initial average = \(\frac{\text{Sum of initial marks}}{\text{Number of students}} = \frac{125}{5} = 25\)

Since 5 grace marks are added to each student's score, the average of the revised marks will be the initial average plus the grace marks.

Revised average = Initial average + Grace marks per student

Revised average = \(25 + 5\)

Revised average = 30

Both methods give the same result, which is 30.

Revision Table: Key Concepts in Calculating Average Marks

Additional Information: Statistics Basics for Average Marks

Calculating the average, or mean, is a fundamental concept in statistics. It gives us a single value that represents a typical score in a dataset, like student marks.

• The average is sensitive to outliers (extremely high or low values).
• Adding a constant to every data point shifts the entire distribution, including the mean, by that constant amount. This is what happened when grace marks were added.
• Multiplying every data point by a constant 'c' would multiply the average by 'c'.
• These properties are useful shortcuts when dealing with data transformations like adding grace marks or converting units.

Understanding how averages change when data is transformed helps in quickly analyzing datasets without recalculating everything from scratch. In this problem, recognizing the property of adding a constant value to each score allowed for a quicker calculation of the revised average marks.