Finding the Third Proportional to 639,408 and 1,400,640

Step by Step Solution

1. Step 1: Write the proportion equation
   639,408 : 1,400,640 = 1,400,640 : x
2. Step 2: Convert to fraction form
   639,408/1,400,640 = 1,400,640/x
3. Step 3: Cross multiply
   639,408x = 1,400,640 × 1,400,640
4. Step 4: Simplify right side
   639,408x = 1,961,792,409,600
5. Step 5: Solve for x
   x = 1,961,792,409,600/639,408
6. Step 6: Final answer
   x = 3,068,138.67