Finding the Fourth Proportional to 1,085.89, 1,629.63 and 811.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,085.89 : 1,629.63 = 811.15 : x
2. Step 2: Convert to fraction form
   1,085.89/1,629.63 = 811.15/x
3. Step 3: Cross multiply
   1,085.89x = 1,629.63 × 811.15
4. Step 4: Simplify right side
   1,085.89x = 1,321,874.37
5. Step 5: Solve for x
   x = 1,321,874.37/1,085.89
6. Step 6: Final answer
   x = 1,217.32