To find the length of the diagonal of a rectangular prism, we can use the formula for the space diagonal \(d\):
\[ d = \sqrt{l^2 + w^2 + h^2} \]
where \(l\) is the length, \(w\) is the width, and \(h\) is the height of the prism.
Given:
- Height \(h = 12 , \text{cm}\)
- Width \(w = 3 , \text{cm}\)
- Length \(l = 4 , \text{cm}\)
Now we substitute the values into the formula:
\[ d = \sqrt{(4)^2 + (3)^2 + (12)^2} \] \[ d = \sqrt{16 + 9 + 144} \] \[ d = \sqrt{169} \] \[ d = 13 , \text{cm} \]
Therefore, the length of the diagonal of the prism is \(13 , \text{cm}\).