In a school, 10% of number of girls is equal to `1/20` th of number of boys. Ratio between the number of boys to number of girls is:

Options

A. `1:2`
B. `2:1`
C. `1:4`
D. `4:1`

Answer

To solve the problem step by step, we start by defining the variables for the number of boys and girls in the school.

### Step 1: Define Variables
Let the number of girls be \( G \) and the number of boys be \( B \).

### Step 2: Set Up the Equation
According to the problem, 10% of the number of girls is equal to \( \frac{1}{20} \) of the number of boys. We can express this mathematically as:
\[ 0.1G = \frac{1}{20}B \]

### Step 3: Simplify the Equation
To eliminate the fraction, we can multiply both sides of the equation by 20:
\[ 20 \times 0.1G = B \]
This simplifies to:
\[ 2G = B \]

### Step 4: Find the Ratio
Now we can find the ratio of the number of boys to the number of girls:
\[ \frac{B}{G} = \frac{2G}{G} = 2 \]
Thus, the ratio of boys to girls is:
\[ B : G = 2 : 1 \]

### Final Answer
The ratio between the number of boys to the number of girls is \( 2 : 1 \).

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