Finding the Third Proportional to 259,206 and 399,870

Step by Step Solution

1. Step 1: Write the proportion equation
   259,206 : 399,870 = 399,870 : x
2. Step 2: Convert to fraction form
   259,206/399,870 = 399,870/x
3. Step 3: Cross multiply
   259,206x = 399,870 × 399,870
4. Step 4: Simplify right side
   259,206x = 159,896,016,900
5. Step 5: Solve for x
   x = 159,896,016,900/259,206
6. Step 6: Final answer
   x = 616,868.50