Finding the Fourth Proportional to 105,728.18, 145,906.90 and 57,978.68

Step by Step Solution

1. Step 1: Write the proportion equation
   105,728.18 : 145,906.90 = 57,978.68 : x
2. Step 2: Convert to fraction form
   105,728.18/145,906.90 = 57,978.68/x
3. Step 3: Cross multiply
   105,728.18x = 145,906.90 × 57,978.68
4. Step 4: Simplify right side
   105,728.18x = 8,459,489,464.89
5. Step 5: Solve for x
   x = 8,459,489,464.89/105,728.18
6. Step 6: Final answer
   x = 80,011.68