What is the average percentage of marks obtained by all the students in subject C and D together.

Options

A. 78
B. 77.53
C. 80.71
D. 79.43

Answer

To find the average percentage of marks obtained by all the students in subjects C and D together, we can follow these steps:

### Step 1: Gather the Data
We have the percentages of marks obtained by 7 students in subjects C and D:
- Subject C: 76, 84, 79, 91, 67, 69, 81
- Subject D: 92, 80, 88, 74, 68, 78, 85

### Step 2: Calculate the Total Marks for Subject C
Add the percentages obtained in subject C:
\[ 76 + 84 + 79 + 91 + 67 + 69 + 81 = 547 \]

### Step 3: Calculate the Total Marks for Subject D
Add the percentages obtained in subject D:
\[ 92 + 80 + 88 + 74 + 68 + 78 + 85 = 565 \]

### Step 4: Calculate the Combined Total Marks
Now, add the total marks from both subjects C and D:
\[ 547 + 565 = 1112 \]

### Step 5: Calculate the Total Number of Students
Since there are 7 students in each subject, the total number of students is:
\[ 7 + 7 = 14 \]

### Step 6: Calculate the Average Percentage
To find the average percentage of marks obtained by all students in subjects C and D together, use the formula for average:
\[ \text{Average} = \frac{\text{Total Marks}}{\text{Total Number of Students}} = \frac{1112}{14} \]
Calculating this gives:
\[ \frac{1112}{14} = 79.42857142857143 \]
Rounding this to two decimal places, we get:
\[ 79.43 \]

### Final Answer
The average percentage of marks obtained by all the students in subjects C and D together is approximately **79.43**.

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