Finding the Fourth Proportional to 1,389.80, 1,918.33 and 800.75

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.80 : 1,918.33 = 800.75 : x
2. Step 2: Convert to fraction form
   1,389.80/1,918.33 = 800.75/x
3. Step 3: Cross multiply
   1,389.80x = 1,918.33 × 800.75
4. Step 4: Simplify right side
   1,389.80x = 1,536,093.16
5. Step 5: Solve for x
   x = 1,536,093.16/1,389.80
6. Step 6: Final answer
   x = 1,105.27