Finding the Fourth Proportional to 2,109.54, 3,164.78 and 811

Step by Step Solution

1. Step 1: Write the proportion equation
   2,109.54 : 3,164.78 = 811 : x
2. Step 2: Convert to fraction form
   2,109.54/3,164.78 = 811/x
3. Step 3: Cross multiply
   2,109.54x = 3,164.78 × 811
4. Step 4: Simplify right side
   2,109.54x = 2,566,636.58
5. Step 5: Solve for x
   x = 2,566,636.58/2,109.54
6. Step 6: Final answer
   x = 1,216.68