Finding the Third Proportional to 640.13 and 978.56

Step by Step Solution

1. Step 1: Write the proportion equation
   640.13 : 978.56 = 978.56 : x
2. Step 2: Convert to fraction form
   640.13/978.56 = 978.56/x
3. Step 3: Cross multiply
   640.13x = 978.56 × 978.56
4. Step 4: Simplify right side
   640.13x = 957,584.57
5. Step 5: Solve for x
   x = 957,584.57/640.13
6. Step 6: Final answer
   x = 1,495.93