Finding the Fourth Proportional to 1,390.16, 1,918.42 and 800.81

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.16 : 1,918.42 = 800.81 : x
2. Step 2: Convert to fraction form
   1,390.16/1,918.42 = 800.81/x
3. Step 3: Cross multiply
   1,390.16x = 1,918.42 × 800.81
4. Step 4: Simplify right side
   1,390.16x = 1,536,276.32
5. Step 5: Solve for x
   x = 1,536,276.32/1,390.16
6. Step 6: Final answer
   x = 1,105.11