Finding the Fourth Proportional to 1,389.90, 1,918.47 and 800.82

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.90 : 1,918.47 = 800.82 : x
2. Step 2: Convert to fraction form
   1,389.90/1,918.47 = 800.82/x
3. Step 3: Cross multiply
   1,389.90x = 1,918.47 × 800.82
4. Step 4: Simplify right side
   1,389.90x = 1,536,349.15
5. Step 5: Solve for x
   x = 1,536,349.15/1,389.90
6. Step 6: Final answer
   x = 1,105.37