Finding the Third Proportional to 639.56 and 978.33

Step by Step Solution

1. Step 1: Write the proportion equation
   639.56 : 978.33 = 978.33 : x
2. Step 2: Convert to fraction form
   639.56/978.33 = 978.33/x
3. Step 3: Cross multiply
   639.56x = 978.33 × 978.33
4. Step 4: Simplify right side
   639.56x = 957,125.92
5. Step 5: Solve for x
   x = 957,125.92/639.56
6. Step 6: Final answer
   x = 1,496.53