Finding the Fourth Proportional to 1,086.15, 1,628.69 and 392.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,086.15 : 1,628.69 = 392.79 : x
2. Step 2: Convert to fraction form
   1,086.15/1,628.69 = 392.79/x
3. Step 3: Cross multiply
   1,086.15x = 1,628.69 × 392.79
4. Step 4: Simplify right side
   1,086.15x = 639,731.18
5. Step 5: Solve for x
   x = 639,731.18/1,086.15
6. Step 6: Final answer
   x = 588.99