Finding the Third Proportional to 427.78 and 640.83

Step by Step Solution

1. Step 1: Write the proportion equation
   427.78 : 640.83 = 640.83 : x
2. Step 2: Convert to fraction form
   427.78/640.83 = 640.83/x
3. Step 3: Cross multiply
   427.78x = 640.83 × 640.83
4. Step 4: Simplify right side
   427.78x = 410,660.69
5. Step 5: Solve for x
   x = 410,660.69/427.78
6. Step 6: Final answer
   x = 959.98