Institution: Bangladesh Shilpa Bank Ltd Exam: Bangladesh Shilpa Bank Ltd - Officer - 2004
Topic: Arithmetic Mathematics (পাটিগণিত), Subject: Mathematics (সাধারণ গণিত)

Best Answer Explained in Below-:

To determine the lowest possible average score for all 15 students when 10 of them scored 75 or more, we should analyze how the scores can be arranged.

First, let's denote the scores of the 10 students who scored 75 or more. To minimize the average of all 15 students, we can assume they each scored exactly 75. This gives a total score from these 10 students of:

\[ 10 \times 75 = 750. \]

Next, we have 5 students whose scores we can minimize to the lowest possible value. Since the test is scored from 0 to 100, the lowest score a student can achieve is 0. So, if all 5 of these students scored 0, their total score would be:

\[ 5 \times 0 = 0. \]

Now, we combine the scores of all 15 students:

\[ \text{Total score} = 750 + 0 = 750. \]

To find the average score, we divide the total score by the number of students:

\[ \text{Average} = \frac{750}{15} = 50. \]

Thus, the lowest possible average score for all 15 students, given the constraints, is indeed 50. This explains why the correct answer is B) 50.