Finding the Fourth Proportional to 2,086.21, 3,129.41 and 787.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,086.21 : 3,129.41 = 787.78 : x
2. Step 2: Convert to fraction form
   2,086.21/3,129.41 = 787.78/x
3. Step 3: Cross multiply
   2,086.21x = 3,129.41 × 787.78
4. Step 4: Simplify right side
   2,086.21x = 2,465,286.61
5. Step 5: Solve for x
   x = 2,465,286.61/2,086.21
6. Step 6: Final answer
   x = 1,181.71