Finding the Fourth Proportional to 1,308.90, 1,805.72 and 811.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,308.90 : 1,805.72 = 811.76 : x
2. Step 2: Convert to fraction form
   1,308.90/1,805.72 = 811.76/x
3. Step 3: Cross multiply
   1,308.90x = 1,805.72 × 811.76
4. Step 4: Simplify right side
   1,308.90x = 1,465,811.72
5. Step 5: Solve for x
   x = 1,465,811.72/1,308.90
6. Step 6: Final answer
   x = 1,119.88