Finding the Third Proportional to 258,984 and 399,978

Step by Step Solution

1. Step 1: Write the proportion equation
   258,984 : 399,978 = 399,978 : x
2. Step 2: Convert to fraction form
   258,984/399,978 = 399,978/x
3. Step 3: Cross multiply
   258,984x = 399,978 × 399,978
4. Step 4: Simplify right side
   258,984x = 159,982,400,484
5. Step 5: Solve for x
   x = 159,982,400,484/258,984
6. Step 6: Final answer
   x = 617,730.83