Finding the Fourth Proportional to 5,781.59, 7,978.59 and 3,128.99

Step by Step Solution

1. Step 1: Write the proportion equation
   5,781.59 : 7,978.59 = 3,128.99 : x
2. Step 2: Convert to fraction form
   5,781.59/7,978.59 = 3,128.99/x
3. Step 3: Cross multiply
   5,781.59x = 7,978.59 × 3,128.99
4. Step 4: Simplify right side
   5,781.59x = 24,964,888.43
5. Step 5: Solve for x
   x = 24,964,888.43/5,781.59
6. Step 6: Final answer
   x = 4,318.00