Finding the Third Proportional to 312,420 and 646,992.75

Step by Step Solution

1. Step 1: Write the proportion equation
   312,420 : 646,992.75 = 646,992.75 : x
2. Step 2: Convert to fraction form
   312,420/646,992.75 = 646,992.75/x
3. Step 3: Cross multiply
   312,420x = 646,992.75 × 646,992.75
4. Step 4: Simplify right side
   312,420x = 418,599,618,552.56
5. Step 5: Solve for x
   x = 418,599,618,552.56/312,420
6. Step 6: Final answer
   x = 1,339,861.78