Finding the Third Proportional to 290,256 and 639,384

Step by Step Solution

1. Step 1: Write the proportion equation
   290,256 : 639,384 = 639,384 : x
2. Step 2: Convert to fraction form
   290,256/639,384 = 639,384/x
3. Step 3: Cross multiply
   290,256x = 639,384 × 639,384
4. Step 4: Simplify right side
   290,256x = 408,811,899,456
5. Step 5: Solve for x
   x = 408,811,899,456/290,256
6. Step 6: Final answer
   x = 1,408,452.88