Finding the Fourth Proportional to 1,389.28, 1,917.12 and 799.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.28 : 1,917.12 = 799.72 : x
2. Step 2: Convert to fraction form
   1,389.28/1,917.12 = 799.72/x
3. Step 3: Cross multiply
   1,389.28x = 1,917.12 × 799.72
4. Step 4: Simplify right side
   1,389.28x = 1,533,159.21
5. Step 5: Solve for x
   x = 1,533,159.21/1,389.28
6. Step 6: Final answer
   x = 1,103.56