Finding the Third Proportional to 642.09 and 908.72

Step by Step Solution

1. Step 1: Write the proportion equation
   642.09 : 908.72 = 908.72 : x
2. Step 2: Convert to fraction form
   642.09/908.72 = 908.72/x
3. Step 3: Cross multiply
   642.09x = 908.72 × 908.72
4. Step 4: Simplify right side
   642.09x = 825,769.77
5. Step 5: Solve for x
   x = 825,769.77/642.09
6. Step 6: Final answer
   x = 1,286.06