Finding the Fourth Proportional to 2,168.31, 3,253.20 and 687.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,168.31 : 3,253.20 = 687.78 : x
2. Step 2: Convert to fraction form
   2,168.31/3,253.20 = 687.78/x
3. Step 3: Cross multiply
   2,168.31x = 3,253.20 × 687.78
4. Step 4: Simplify right side
   2,168.31x = 2,237,469.63
5. Step 5: Solve for x
   x = 2,237,469.63/2,168.31
6. Step 6: Final answer
   x = 1,031.90