Institution: Bangladesh Bank Exam: Officer (General) |-Sonali | Janata | Bangladesh Krishi_Bangladesh Development bank ২৪.০৫.২০১৯ ||
Topic: Arithmetic Mathematics (পাটিগণিত), Subject: Mathematics (সাধারণ গণিত)

Best Answer Explained in Below-:

To determine the employee's monthly salary before the increase, we can use the information provided about the salary increase. If the employee received a 10% monthly increase which led to an annual increase of TK. 9000, we need to find out what the salary was before the increase.

Let’s denote the initial monthly salary as \( x \). The 10% increase on this salary would then be \( 0.10x \) per month. Consequently, the new monthly salary after the increase is \( x + 0.10x = 1.10x \).

The increase in salary per month can be calculated as:
\[
\text{Increase per month} = 0.10x
\]
Over a year (12 months), this results in:
\[
\text{Annual increase} = 12 \times 0.10x = 1.2x
\]
According to the problem, this annual increase equals TK. 9000:
\[
1.2x = 9000
\]
Now we solve for \( x \) (the initial monthly salary):
\[
x = \frac{9000}{1.2} = 7500
\]

Thus, the employee's monthly salary before the increase was TK. 7500, making option C the correct answer.