Finding the Third Proportional to 485.50 and 664.50

Step by Step Solution

1. Step 1: Write the proportion equation
   485.50 : 664.50 = 664.50 : x
2. Step 2: Convert to fraction form
   485.50/664.50 = 664.50/x
3. Step 3: Cross multiply
   485.50x = 664.50 × 664.50
4. Step 4: Simplify right side
   485.50x = 441,560.25
5. Step 5: Solve for x
   x = 441,560.25/485.50
6. Step 6: Final answer
   x = 909.50