Finding the Fourth Proportional to 85,890.88, 128,590.56 and 58,139.20

Step by Step Solution

1. Step 1: Write the proportion equation
   85,890.88 : 128,590.56 = 58,139.20 : x
2. Step 2: Convert to fraction form
   85,890.88/128,590.56 = 58,139.20/x
3. Step 3: Cross multiply
   85,890.88x = 128,590.56 × 58,139.20
4. Step 4: Simplify right side
   85,890.88x = 7,476,152,285.95
5. Step 5: Solve for x
   x = 7,476,152,285.95/85,890.88
6. Step 6: Final answer
   x = 87,042.45