Finding the Fourth Proportional to 1,390.28, 1,918.55 and 800.87

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.28 : 1,918.55 = 800.87 : x
2. Step 2: Convert to fraction form
   1,390.28/1,918.55 = 800.87/x
3. Step 3: Cross multiply
   1,390.28x = 1,918.55 × 800.87
4. Step 4: Simplify right side
   1,390.28x = 1,536,501.55
5. Step 5: Solve for x
   x = 1,536,501.55/1,390.28
6. Step 6: Final answer
   x = 1,105.18