Finding the Third Proportional to 558.50 and 618.50

Step by Step Solution

1. Step 1: Write the proportion equation
   558.50 : 618.50 = 618.50 : x
2. Step 2: Convert to fraction form
   558.50/618.50 = 618.50/x
3. Step 3: Cross multiply
   558.50x = 618.50 × 618.50
4. Step 4: Simplify right side
   558.50x = 382,542.25
5. Step 5: Solve for x
   x = 382,542.25/558.50
6. Step 6: Final answer
   x = 684.95