Finding the Fourth Proportional to 787.12, 1,086.42 and 492.72

Step by Step Solution

1. Step 1: Write the proportion equation
   787.12 : 1,086.42 = 492.72 : x
2. Step 2: Convert to fraction form
   787.12/1,086.42 = 492.72/x
3. Step 3: Cross multiply
   787.12x = 1,086.42 × 492.72
4. Step 4: Simplify right side
   787.12x = 535,300.86
5. Step 5: Solve for x
   x = 535,300.86/787.12
6. Step 6: Final answer
   x = 680.08