Finding the Third Proportional to 321,672 and 687,648

Step by Step Solution

1. Step 1: Write the proportion equation
   321,672 : 687,648 = 687,648 : x
2. Step 2: Convert to fraction form
   321,672/687,648 = 687,648/x
3. Step 3: Cross multiply
   321,672x = 687,648 × 687,648
4. Step 4: Simplify right side
   321,672x = 472,859,771,904
5. Step 5: Solve for x
   x = 472,859,771,904/321,672
6. Step 6: Final answer
   x = 1,470,006.01