Finding the Fourth Proportional to 85,912.36, 128,800.50 and 39,139.72

Step by Step Solution

1. Step 1: Write the proportion equation
   85,912.36 : 128,800.50 = 39,139.72 : x
2. Step 2: Convert to fraction form
   85,912.36/128,800.50 = 39,139.72/x
3. Step 3: Cross multiply
   85,912.36x = 128,800.50 × 39,139.72
4. Step 4: Simplify right side
   85,912.36x = 5,041,215,505.86
5. Step 5: Solve for x
   x = 5,041,215,505.86/85,912.36
6. Step 6: Final answer
   x = 58,678.58