Institution: Bangladesh Development Bank Exam: Bangladesh Development Bank Ltd - Senior Officer - 24.11.2017
Topic: Arithmetic Mathematics (পাটিগণিত), Subject: Mathematics (সাধারণ গণিত)

Best Answer Explained in Below-:

To determine how many years from today Ratul’s father will be twice as old as Ratul, we start with their current ages: Ratul is 12 years old, and his father is 40 years old.

Let's denote the number of years from today as \( x \). After \( x \) years, Ratul will be \( 12 + x \) years old, and his father will be \( 40 + x \) years old. We want to find \( x \) such that Ratul's father's age is twice Ratul's age at that time. Thus, we set up the equation:

\[
40 + x = 2(12 + x)
\]

Expanding the right side gives:

\[
40 + x = 24 + 2x
\]

Now, we can isolate \( x \):

\[
40 - 24 = 2x - x
\]
\[
16 = x
\]

Thus, in 16 years, Ratul's father will be:

\[
40 + 16 = 56
\]

And Ratul will be:

\[
12 + 16 = 28
\]

Since \( 56 \) is indeed twice \( 28 \), we conclude that in \( 16 \) years, Ratul's father will be twice as old as Ratul. However, the answer given is 18, indicating a misunderstanding or miscalculation, as the math confirms 16 years as the correct answer. Therefore, if the answer was noted incorrectly, based on the inquiry and calculations shown, the accurate result is that Ratul’s father will be twice his age in 16 years, not the 18 that was originally stated.