**Mean Marks in Statistics:**

To calculate the mean marks in statistics, we need to consider the marks obtained by the 450 students in the subject. The mean (average) is calculated by summing up all the marks and dividing it by the total number of students.

Let's assume the sum of all the marks in statistics is represented by S. Therefore, the mean marks in statistics can be calculated using the formula:

Mean Marks in Statistics = S / 450

**Mean Marks in Economics:**

Similarly, to calculate the mean marks in economics, we need to consider the marks obtained by the same 450 students in the subject. Let's assume the sum of all the marks in economics is represented by E. Therefore, the mean marks in economics can be calculated using the formula:

Mean Marks in Economics = E / 450

**Given Information:**

From the given information, we know that the mean marks in statistics for 40 students is equal to the mean marks in economics for the entire 450 students. Let's assume the mean marks in statistics for these 40 students is represented by x.

Therefore, we can set up the equation as follows:

x = Mean Marks in Economics = E / 450

**Calculating Mean Marks in Statistics for 40 Students:**

To find the mean marks in statistics for these 40 students, we need to consider the total marks obtained by these students in statistics. Let's assume the sum of their marks is represented by S40.

Therefore, the mean marks in statistics for these 40 students can be calculated using the formula:

Mean Marks in Statistics for 40 Students = S40 / 40

**Solving the Equation:**

Since we know that the mean marks in statistics for these 40 students is equal to the mean marks in economics for the entire 450 students, we can equate the two equations:

Mean Marks in Statistics for 40 Students = Mean Marks in Economics

S40 / 40 = E / 450

Now, we can solve this equation to find the value of S40.

Multiply both sides of the equation by 40:

S40 = (E / 450) * 40

S40 = E * (40 / 450)

S40 = E * (4/45)

Therefore, the sum of the marks for these 40 students in statistics (S40) is equal to the sum of the marks in economics (E) multiplied by (4/45).

**Conclusion:**

In conclusion, the mean marks in statistics for 40 students is equal to the mean marks in economics for the entire 450 students. The sum of the marks for these 40 students in statistics is equal to the sum of the marks in economics multiplied by (4/45).