**Given Information:**
- The area of triangle ABC is 48 cm^2.
- The height of triangle ABC is 4 cm.

**To Find:**
- The length of BC.

**Solution:**

Let's denote the base of the triangle as BC, the height as h, and the area as A.

1. **Understanding the Formula:**
- The area of a triangle is given by the formula: A = (1/2) * base * height.
- In this case, we have the area (A) and the height (h), and we need to find the base (BC).

2. **Applying the Formula:**
- Substituting the given values into the formula, we have:
48 cm^2 = (1/2) * BC * 4 cm.

3. **Simplifying the Equation:**
- Multiplying both sides of the equation by 2 to remove the fraction, we get:
96 cm^2 = BC * 4 cm.

4. **Solving for BC:**
- Dividing both sides of the equation by 4 cm, we find:
BC = 96 cm^2 / 4 cm.
BC = 24 cm.

5. **Final Answer:**
- The length of BC is 24 cm.

Therefore, the length of BC is 24 cm.