Finding the Third Proportional to 328.78 and 355.78

Step by Step Solution

1. Step 1: Write the proportion equation
   328.78 : 355.78 = 355.78 : x
2. Step 2: Convert to fraction form
   328.78/355.78 = 355.78/x
3. Step 3: Cross multiply
   328.78x = 355.78 × 355.78
4. Step 4: Simplify right side
   328.78x = 126,580.30
5. Step 5: Solve for x
   x = 126,580.30/328.78
6. Step 6: Final answer
   x = 385.00