Finding the Fourth Proportional to 1,105.90, 1,659.89 and 809.71

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.90 : 1,659.89 = 809.71 : x
2. Step 2: Convert to fraction form
   1,105.90/1,659.89 = 809.71/x
3. Step 3: Cross multiply
   1,105.90x = 1,659.89 × 809.71
4. Step 4: Simplify right side
   1,105.90x = 1,344,027.41
5. Step 5: Solve for x
   x = 1,344,027.41/1,105.90
6. Step 6: Final answer
   x = 1,215.33