Finding the Third Proportional to 644.63 and 978.75

Step by Step Solution

1. Step 1: Write the proportion equation
   644.63 : 978.75 = 978.75 : x
2. Step 2: Convert to fraction form
   644.63/978.75 = 978.75/x
3. Step 3: Cross multiply
   644.63x = 978.75 × 978.75
4. Step 4: Simplify right side
   644.63x = 957,951.56
5. Step 5: Solve for x
   x = 957,951.56/644.63
6. Step 6: Final answer
   x = 1,486.06