Finding the Third Proportional to 217.69 and 388.69

Step by Step Solution

1. Step 1: Write the proportion equation
   217.69 : 388.69 = 388.69 : x
2. Step 2: Convert to fraction form
   217.69/388.69 = 388.69/x
3. Step 3: Cross multiply
   217.69x = 388.69 × 388.69
4. Step 4: Simplify right side
   217.69x = 151,077.97
5. Step 5: Solve for x
   x = 151,077.97/217.69
6. Step 6: Final answer
   x = 694.01