Finding the Third Proportional to 399.50 and 810.25

Step by Step Solution

1. Step 1: Write the proportion equation
   399.50 : 810.25 = 810.25 : x
2. Step 2: Convert to fraction form
   399.50/810.25 = 810.25/x
3. Step 3: Cross multiply
   399.50x = 810.25 × 810.25
4. Step 4: Simplify right side
   399.50x = 656,505.06
5. Step 5: Solve for x
   x = 656,505.06/399.50
6. Step 6: Final answer
   x = 1,643.32