Finding the Fourth Proportional to 1,398.25, 1,929.61 and 800.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.25 : 1,929.61 = 800.80 : x
2. Step 2: Convert to fraction form
   1,398.25/1,929.61 = 800.80/x
3. Step 3: Cross multiply
   1,398.25x = 1,929.61 × 800.80
4. Step 4: Simplify right side
   1,398.25x = 1,545,231.69
5. Step 5: Solve for x
   x = 1,545,231.69/1,398.25
6. Step 6: Final answer
   x = 1,105.12