Finding the Third Proportional to 399.75 and 557.38

Step by Step Solution

1. Step 1: Write the proportion equation
   399.75 : 557.38 = 557.38 : x
2. Step 2: Convert to fraction form
   399.75/557.38 = 557.38/x
3. Step 3: Cross multiply
   399.75x = 557.38 × 557.38
4. Step 4: Simplify right side
   399.75x = 310,666.89
5. Step 5: Solve for x
   x = 310,666.89/399.75
6. Step 6: Final answer
   x = 777.15