Finding the Third Proportional to 256,405 and 398,049

Step by Step Solution

1. Step 1: Write the proportion equation
   256,405 : 398,049 = 398,049 : x
2. Step 2: Convert to fraction form
   256,405/398,049 = 398,049/x
3. Step 3: Cross multiply
   256,405x = 398,049 × 398,049
4. Step 4: Simplify right side
   256,405x = 158,443,006,401
5. Step 5: Solve for x
   x = 158,443,006,401/256,405
6. Step 6: Final answer
   x = 617,940.39