To find the width of a right rectangular prism, you can use the formula for the volume of a rectangular prism:
\[ \text{Volume} = \text{length} \times \text{width} \times \text{height} \]
Given that the volume is 1,000, the height is 10, and the length is 20, we can set up the formula:
\[ 1,000 = 20 \times \text{width} \times 10 \]
Now, simplify the equation:
\[ 1,000 = 200 \times \text{width} \]
Next, divide both sides by 200 to solve for width:
\[ \text{width} = \frac{1,000}{200} = 5 \]
Therefore, the width of the prism is 5.