Problem 1229

1. First, calculate the volume of the two-inch cube. The volume $V$ of a cube with side length $s$ is given by:
$$V = s^3$$
For a two-inch cube:
$$V = 2^3 = 8 \text{ cubic inches}$$

2. We know that this two-inch cube weighs 3 pounds and is worth $200. Therefore, the value per cubic inch of silver can be calculated as:
$$\text{Value per cubic inch} = \frac{200 \text{ dollars}}{8 \text{ cubic inches}} = 25 \text{ dollars per cubic inch}$$

3. Next, calculate the volume of the three-inch cube:
$$V = 3^3 = 27 \text{ cubic inches}$$

4. To find the value of the three-inch cube, multiply the volume of the three-inch cube by the value per cubic inch:
$$\text{Value of three-inch cube} = 27 \text{ cubic inches} \times 25 \text{ dollars per cubic inch} = 675 \text{ dollars}$$

Conclusion:
$$\boxed{675 \text{ dollars}}$$