In a class of 60, the number of girls are twice that of boys. Kamal ranked seventeenth from the top. If there are nine girls ahead of Kamal, how many boys are after him in rank?

Options

A. 3
B. 7
C. 12
D. 23

Explanation

To solve the problem step by step, we will follow the information given in the question:

1. **Determine the number of boys and girls in the class:**
- Let the number of boys be \( x \).
- Then, the number of girls will be \( 2x \) (since the number of girls is twice that of boys).
- The total number of students in the class is given as 60.
- Therefore, we can set up the equation:
\[ x + 2x = 60 \]
- This simplifies to:
\[ 3x = 60 \]
- Dividing both sides by 3 gives:
\[ x = 20 \]
- Thus, the number of boys is 20 and the number of girls is:
\[ 2x = 2 \times 20 = 40 \]

2. **Analyze Kamal's ranking:**
- Kamal is ranked 17th from the top.
- There are 9 girls ahead of Kamal.

3. **Calculate the number of students behind Kamal:**
- Since Kamal is ranked 17th, the number of students behind him is:
\[ 60 - 17 = 43 \]

4. **Determine the number of girls behind Kamal:**
- If there are 9 girls ahead of Kamal, the total number of girls in the class is 40.
- Therefore, the number of girls behind Kamal is:
\[ 40 - 9 = 31 \]

5. **Calculate the number of boys behind Kamal:**
- The total number of students behind Kamal is 43.
- Out of these, 31 are girls. Therefore, the number of boys behind Kamal is:
\[ 43 - 31 = 12 \]

Thus, the final answer is that there are **12 boys** after Kamal in rank.