Finding the Fourth Proportional to 80.15, 109.89 and 78.69

Step by Step Solution

1. Step 1: Write the proportion equation
   80.15 : 109.89 = 78.69 : x
2. Step 2: Convert to fraction form
   80.15/109.89 = 78.69/x
3. Step 3: Cross multiply
   80.15x = 109.89 × 78.69
4. Step 4: Simplify right side
   80.15x = 8,647.62
5. Step 5: Solve for x
   x = 8,647.62/80.15
6. Step 6: Final answer
   x = 107.89