Finding the Third Proportional to 310.50 and 661.50

Step by Step Solution

1. Step 1: Write the proportion equation
   310.50 : 661.50 = 661.50 : x
2. Step 2: Convert to fraction form
   310.50/661.50 = 661.50/x
3. Step 3: Cross multiply
   310.50x = 661.50 × 661.50
4. Step 4: Simplify right side
   310.50x = 437,582.25
5. Step 5: Solve for x
   x = 437,582.25/310.50
6. Step 6: Final answer
   x = 1,409.28