Finding the Third Proportional to 311,989.50 and 638,760

Step by Step Solution

1. Step 1: Write the proportion equation
   311,989.50 : 638,760 = 638,760 : x
2. Step 2: Convert to fraction form
   311,989.50/638,760 = 638,760/x
3. Step 3: Cross multiply
   311,989.50x = 638,760 × 638,760
4. Step 4: Simplify right side
   311,989.50x = 408,014,337,600
5. Step 5: Solve for x
   x = 408,014,337,600/311,989.50
6. Step 6: Final answer
   x = 1,307,782.27