Finding the Third Proportional to 398.50 and 865.50

Step by Step Solution

1. Step 1: Write the proportion equation
   398.50 : 865.50 = 865.50 : x
2. Step 2: Convert to fraction form
   398.50/865.50 = 865.50/x
3. Step 3: Cross multiply
   398.50x = 865.50 × 865.50
4. Step 4: Simplify right side
   398.50x = 749,090.25
5. Step 5: Solve for x
   x = 749,090.25/398.50
6. Step 6: Final answer
   x = 1,879.77