Finding the Fourth Proportional to 1,389.86, 1,918.20 and 800.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.86 : 1,918.20 = 800.28 : x
2. Step 2: Convert to fraction form
   1,389.86/1,918.20 = 800.28/x
3. Step 3: Cross multiply
   1,389.86x = 1,918.20 × 800.28
4. Step 4: Simplify right side
   1,389.86x = 1,535,097.10
5. Step 5: Solve for x
   x = 1,535,097.10/1,389.86
6. Step 6: Final answer
   x = 1,104.50