Finding the Third Proportional to 640.69 and 1,393.88

Step by Step Solution

1. Step 1: Write the proportion equation
   640.69 : 1,393.88 = 1,393.88 : x
2. Step 2: Convert to fraction form
   640.69/1,393.88 = 1,393.88/x
3. Step 3: Cross multiply
   640.69x = 1,393.88 × 1,393.88
4. Step 4: Simplify right side
   640.69x = 1,942,887.52
5. Step 5: Solve for x
   x = 1,942,887.52/640.69
6. Step 6: Final answer
   x = 3,032.50