David obtained 76, 65, 82, 67 and 85 marks out of 100 in English, Mathematics, Physics, Chemistry and Biology respectively. What are his average marks across these five subjects?

Introduction / Context:
This question is a straightforward average marks problem that checks whether you can correctly sum several values and then divide by the number of observations. It represents a typical scenario from school examinations where a student obtains different marks in different subjects and we need to compute the overall performance in terms of average marks.

Given Data / Assumptions:

The subjects are English, Mathematics, Physics, Chemistry and Biology.
Marks obtained are 76, 65, 82, 67 and 85 respectively, each out of 100.
We must find the average of these five marks.
All marks are treated equally with no different weightage for any subject.

Concept / Approach:
The concept of average is simple: average = total sum of observations divided by the number of observations. Here we add the five subject marks and divide the total by 5. No complex formula is needed, but accuracy in addition and division is crucial to arrive at the correct answer.

Step-by-Step Solution:
Step 1: List the marks clearly. English = 76, Mathematics = 65, Physics = 82, Chemistry = 67, Biology = 85. Step 2: Add all the marks. Total marks = 76 + 65 + 82 + 67 + 85. Compute this sum: 76 + 65 = 141, 141 + 82 = 223, 223 + 67 = 290, 290 + 85 = 375. So, total marks = 375. Step 3: Divide by the number of subjects. Number of subjects = 5. Average marks = total marks / number of subjects = 375 / 5 = 75.

Verification / Alternative Check:
We can quickly verify the division: 5 * 75 = 375, which matches the total marks computed earlier. The average 75 is also reasonable given that most individual marks (76, 82, 85) are above 70 and only one mark is slightly lower at 65, so an overall average in the mid seventies is logically consistent.

Why Other Options Are Wrong:
Option 68 would give a total of 68 * 5 = 340, which is much less than the actual total of 375.
Option 65 would correspond to 65 * 5 = 325, which is again below the true sum and does not reflect the higher marks in Physics and Biology.
Option 60 would give a total of 300, which is far away from the actual total and therefore clearly incorrect.

Common Pitfalls:
Mistakes usually come from wrong addition of the five marks or from dividing by an incorrect number of subjects. Sometimes students also misread one of the marks or miss one subject entirely when adding. Double checking the sum and ensuring you divide by exactly 5 avoids these errors.

Final Answer:
David’s average marks across the five subjects are 75.