Finding the Fourth Proportional to 105.81, 145.83 and 78.09

Step by Step Solution

1. Step 1: Write the proportion equation
   105.81 : 145.83 = 78.09 : x
2. Step 2: Convert to fraction form
   105.81/145.83 = 78.09/x
3. Step 3: Cross multiply
   105.81x = 145.83 × 78.09
4. Step 4: Simplify right side
   105.81x = 11,387.86
5. Step 5: Solve for x
   x = 11,387.86/105.81
6. Step 6: Final answer
   x = 107.63