ABCD is rectangle whose three vertices are B(4, 0), C(4, 3) and D(0, 3). Find the length of one of its diagonal.

Explanation

To find the length of one of the diagonals of rectangle ABCD, we can use the distance formula. The vertices we have are B(4, 0), C(4, 3), and D(0, 3). We need to find the coordinates of point A to complete the rectangle.

### Step-by-Step Solution:

1. **Identify the Coordinates of Points:**
- We have B(4, 0), C(4, 3), and D(0, 3).
- Since B and C share the same x-coordinate, they are vertically aligned.
- D and C share the same y-coordinate, indicating that they are horizontally aligned.

2. **Find the Coordinates of Point A:**
- Point A will have the same y-coordinate as point B and the same x-coordinate as point D.
- Therefore, the coordinates of point A will be A(0, 0).

3. **Choose One Diagonal to Calculate:**
- We can calculate the length of diagonal AC or BD. Here, we will calculate the length of diagonal AC.

4. **Use the Distance Formula:**
- The distance formula is given by:
\[ d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \]
- For diagonal AC, we have:
- A(0, 0) as (x1, y1)
- C(4, 3) as (x2, y2)

5. **Substitute the Coordinates into the Formula:**
\[ d = \sqrt{(4 - 0)^2 + (3 - 0)^2} \]
\[ d = \sqrt{4^2 + 3^2} \]
\[ d = \sqrt{16 + 9} \]
\[ d = \sqrt{25} \]

6. **Calculate the Length of the Diagonal:**
\[ d = 5 \]

### Final Answer:
The length of one of the diagonals of rectangle ABCD is **5 units**.