Finding the Third Proportional to 309,468 and 678,672

Step by Step Solution

1. Step 1: Write the proportion equation
   309,468 : 678,672 = 678,672 : x
2. Step 2: Convert to fraction form
   309,468/678,672 = 678,672/x
3. Step 3: Cross multiply
   309,468x = 678,672 × 678,672
4. Step 4: Simplify right side
   309,468x = 460,595,683,584
5. Step 5: Solve for x
   x = 460,595,683,584/309,468
6. Step 6: Final answer
   x = 1,488,346.72