Finding the Third Proportional to 309,726.75 and 685,780.50

Step by Step Solution

1. Step 1: Write the proportion equation
   309,726.75 : 685,780.50 = 685,780.50 : x
2. Step 2: Convert to fraction form
   309,726.75/685,780.50 = 685,780.50/x
3. Step 3: Cross multiply
   309,726.75x = 685,780.50 × 685,780.50
4. Step 4: Simplify right side
   309,726.75x = 470,294,894,180.25
5. Step 5: Solve for x
   x = 470,294,894,180.25/309,726.75
6. Step 6: Final answer
   x = 1,518,418.72