Finding the Fourth Proportional to 1,389.27, 1,917.21 and 799.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.27 : 1,917.21 = 799.80 : x
2. Step 2: Convert to fraction form
   1,389.27/1,917.21 = 799.80/x
3. Step 3: Cross multiply
   1,389.27x = 1,917.21 × 799.80
4. Step 4: Simplify right side
   1,389.27x = 1,533,384.56
5. Step 5: Solve for x
   x = 1,533,384.56/1,389.27
6. Step 6: Final answer
   x = 1,103.73