To find the longer side of the similar rectangle, we can use the property of similar rectangles that their corresponding sides are in proportion.
Given:
- Dimensions of the original rectangle: 8 cm (shorter side) and 12 cm (longer side).
- Shorter side of the similar rectangle: 6 cm.
Let's denote:
- The longer side of the similar rectangle as \( x \).
Since the rectangles are similar, we can set up a proportion between the sides of the rectangles:
\[ \frac{\text{shorter side of similar rectangle}}{\text{shorter side of original rectangle}} = \frac{\text{longer side of similar rectangle}}{\text{longer side of original rectangle}} \]
This can be written as:
\[ \frac{6}{8} = \frac{x}{12} \]
Now, we can cross-multiply to solve for \( x \):
\[ 6 \times 12 = 8 \times x \]
\[ 72 = 8x \]
Now, divide both sides by 8:
\[ x = \frac{72}{8} = 9 \]
Thus, the longer side of the similar rectangle is \( 9 \) cm.
The answer is 9 cm.