Finding the Third Proportional to 218.50 and 389.50

Step by Step Solution

1. Step 1: Write the proportion equation
   218.50 : 389.50 = 389.50 : x
2. Step 2: Convert to fraction form
   218.50/389.50 = 389.50/x
3. Step 3: Cross multiply
   218.50x = 389.50 × 389.50
4. Step 4: Simplify right side
   218.50x = 151,710.25
5. Step 5: Solve for x
   x = 151,710.25/218.50
6. Step 6: Final answer
   x = 694.33