Finding the Fourth Proportional to 1,389.20, 1,917.55 and 799.88

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.20 : 1,917.55 = 799.88 : x
2. Step 2: Convert to fraction form
   1,389.20/1,917.55 = 799.88/x
3. Step 3: Cross multiply
   1,389.20x = 1,917.55 × 799.88
4. Step 4: Simplify right side
   1,389.20x = 1,533,798.31
5. Step 5: Solve for x
   x = 1,533,798.31/1,389.20
6. Step 6: Final answer
   x = 1,104.09