Finding the Third Proportional to 321,138 and 678,456

Step by Step Solution

1. Step 1: Write the proportion equation
   321,138 : 678,456 = 678,456 : x
2. Step 2: Convert to fraction form
   321,138/678,456 = 678,456/x
3. Step 3: Cross multiply
   321,138x = 678,456 × 678,456
4. Step 4: Simplify right side
   321,138x = 460,302,543,936
5. Step 5: Solve for x
   x = 460,302,543,936/321,138
6. Step 6: Final answer
   x = 1,433,348.11