Finding the Fourth Proportional to 1,390.22, 1,918.54 and 800.74

Step by Step Solution

1. Step 1: Write the proportion equation
   1,390.22 : 1,918.54 = 800.74 : x
2. Step 2: Convert to fraction form
   1,390.22/1,918.54 = 800.74/x
3. Step 3: Cross multiply
   1,390.22x = 1,918.54 × 800.74
4. Step 4: Simplify right side
   1,390.22x = 1,536,251.72
5. Step 5: Solve for x
   x = 1,536,251.72/1,390.22
6. Step 6: Final answer
   x = 1,105.05