Finding the Third Proportional to 399,440 and 561,839

Step by Step Solution

1. Step 1: Write the proportion equation
   399,440 : 561,839 = 561,839 : x
2. Step 2: Convert to fraction form
   399,440/561,839 = 561,839/x
3. Step 3: Cross multiply
   399,440x = 561,839 × 561,839
4. Step 4: Simplify right side
   399,440x = 315,663,061,921
5. Step 5: Solve for x
   x = 315,663,061,921/399,440
6. Step 6: Final answer
   x = 790,264.02