Finding the Third Proportional to 256.31 and 408.42

Step by Step Solution

1. Step 1: Write the proportion equation
   256.31 : 408.42 = 408.42 : x
2. Step 2: Convert to fraction form
   256.31/408.42 = 408.42/x
3. Step 3: Cross multiply
   256.31x = 408.42 × 408.42
4. Step 4: Simplify right side
   256.31x = 166,808.43
5. Step 5: Solve for x
   x = 166,808.43/256.31
6. Step 6: Final answer
   x = 650.80