Finding the Third Proportional to 399.38 and 864.38

Step by Step Solution

1. Step 1: Write the proportion equation
   399.38 : 864.38 = 864.38 : x
2. Step 2: Convert to fraction form
   399.38/864.38 = 864.38/x
3. Step 3: Cross multiply
   399.38x = 864.38 × 864.38
4. Step 4: Simplify right side
   399.38x = 747,144.14
5. Step 5: Solve for x
   x = 747,144.14/399.38
6. Step 6: Final answer
   x = 1,870.78