If a = 2b, then a:b = ____.

Options

A. `2:1`
B. `1:2`
C. `3:4`
D. `4:3`

Explanation

To solve the problem where \( a = 2b \) and we need to find the ratio \( a:b \), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the given relationship**: We are given that \( a = 2b \). This means that \( a \) is twice the value of \( b \).

2. **Express the ratio**: The ratio \( a:b \) can be expressed as \( \frac{a}{b} \).

3. **Substitute the value of \( a \)**: Since \( a = 2b \), we can substitute \( 2b \) for \( a \) in the ratio:
\[ a:b = \frac{a}{b} = \frac{2b}{b} \]

4. **Simplify the ratio**: When we simplify \( \frac{2b}{b} \), the \( b \) in the numerator and denominator cancels out (assuming \( b \neq 0 \)):
\[ \frac{2b}{b} = 2 \]

5. **Write the ratio in standard form**: The simplified ratio can be written as:
\[ a:b = 2:1 \]

### Final Answer:
Thus, the ratio \( a:b \) is \( 2:1 \).

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