Finding the Third Proportional to 256.69 and 391.69

Step by Step Solution

1. Step 1: Write the proportion equation
   256.69 : 391.69 = 391.69 : x
2. Step 2: Convert to fraction form
   256.69/391.69 = 391.69/x
3. Step 3: Cross multiply
   256.69x = 391.69 × 391.69
4. Step 4: Simplify right side
   256.69x = 153,419.10
5. Step 5: Solve for x
   x = 153,419.10/256.69
6. Step 6: Final answer
   x = 597.69