Finding the Third Proportional to 6,399 and 12,978

Step by Step Solution

1. Step 1: Write the proportion equation
   6,399 : 12,978 = 12,978 : x
2. Step 2: Convert to fraction form
   6,399/12,978 = 12,978/x
3. Step 3: Cross multiply
   6,399x = 12,978 × 12,978
4. Step 4: Simplify right side
   6,399x = 168,428,484
5. Step 5: Solve for x
   x = 168,428,484/6,399
6. Step 6: Final answer
   x = 26,321.06