`70%` of students in a school are boys, if the number of girls is 240, how many boys are there in the school?

Options

A. 420
B. 560
C. 630
D. 480

Answer

To find out how many boys are in the school, we can follow these steps:

### Step 1: Understand the given information
We know that 70% of the students in the school are boys, and the number of girls is 240.

### Step 2: Calculate the percentage of girls
Since 70% of the students are boys, the remaining percentage must be girls.
- Percentage of girls = 100% - 70% = 30%

### Step 3: Set up the equation
Let the total number of students in the school be represented by \( x \). According to the information given, 30% of the total students are girls. Therefore, we can write the equation:
\[ 0.30x = 240 \]

### Step 4: Solve for \( x \)
To find \( x \), divide both sides of the equation by 0.30:
\[ x = \frac{240}{0.30} \]
\[ x = 800 \]

### Step 5: Calculate the number of boys
Now that we have the total number of students, we can find the number of boys. Since 70% of the students are boys:
\[ \text{Number of boys} = 0.70 \times 800 \]
\[ \text{Number of boys} = 560 \]

### Conclusion
Therefore, the number of boys in the school is **560**.

---