Finding the Fourth Proportional to 1,390.27, 1,918.59 and 800.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.27 : 1,918.59 = 800.80 : x
2. Step 2: Convert to fraction form
   1,390.27/1,918.59 = 800.80/x
3. Step 3: Cross multiply
   1,390.27x = 1,918.59 × 800.80
4. Step 4: Simplify right side
   1,390.27x = 1,536,406.87
5. Step 5: Solve for x
   x = 1,536,406.87/1,390.27
6. Step 6: Final answer
   x = 1,105.11