Finding the Fourth Proportional to 76.91, 105.89 and 66.69

Step by Step Solution

1. Step 1: Write the proportion equation
   76.91 : 105.89 = 66.69 : x
2. Step 2: Convert to fraction form
   76.91/105.89 = 66.69/x
3. Step 3: Cross multiply
   76.91x = 105.89 × 66.69
4. Step 4: Simplify right side
   76.91x = 7,061.47
5. Step 5: Solve for x
   x = 7,061.47/76.91
6. Step 6: Final answer
   x = 91.81