The ratio of the length of a field to its width is 5:3. Find its length if the width is 42 metres.

Answer

To solve the problem, we need to find the length of a field given the ratio of its length to width and the width itself.

### Step-by-Step Solution:

1. **Understand the Ratio**: The ratio of the length (L) to the width (W) of the field is given as 5:3. This means:
\[ \frac{L}{W} = \frac{5}{3} \]

2. **Identify the Given Information**: We know the width (W) of the field is 42 meters. So, we can write:
\[ W = 42 \text{ meters} \]

3. **Set Up the Equation**: Using the ratio, we can express the length in terms of the width:
\[ L = \frac{5}{3} \times W \]

4. **Substitute the Width**: Now, substitute the value of the width (W = 42 meters) into the equation:
\[ L = \frac{5}{3} \times 42 \]

5. **Calculate the Length**: First, calculate \( \frac{42}{3} \):
\[ \frac{42}{3} = 14 \]
Now, multiply by 5:
\[ L = 5 \times 14 = 70 \]

6. **Final Answer**: Therefore, the length of the field is:
\[ L = 70 \text{ meters} \]