Finding the Third Proportional to 255.50 and 406.50

Step by Step Solution

1. Step 1: Write the proportion equation
   255.50 : 406.50 = 406.50 : x
2. Step 2: Convert to fraction form
   255.50/406.50 = 406.50/x
3. Step 3: Cross multiply
   255.50x = 406.50 × 406.50
4. Step 4: Simplify right side
   255.50x = 165,242.25
5. Step 5: Solve for x
   x = 165,242.25/255.50
6. Step 6: Final answer
   x = 646.74