Finding the Third Proportional to 642.94 and 1,399.78

Step by Step Solution

1. Step 1: Write the proportion equation
   642.94 : 1,399.78 = 1,399.78 : x
2. Step 2: Convert to fraction form
   642.94/1,399.78 = 1,399.78/x
3. Step 3: Cross multiply
   642.94x = 1,399.78 × 1,399.78
4. Step 4: Simplify right side
   642.94x = 1,959,387.55
5. Step 5: Solve for x
   x = 1,959,387.55/642.94
6. Step 6: Final answer
   x = 3,047.56