Finding the Third Proportional to 7,916 and 12,978

Step by Step Solution

1. Step 1: Write the proportion equation
   7,916 : 12,978 = 12,978 : x
2. Step 2: Convert to fraction form
   7,916/12,978 = 12,978/x
3. Step 3: Cross multiply
   7,916x = 12,978 × 12,978
4. Step 4: Simplify right side
   7,916x = 168,428,484
5. Step 5: Solve for x
   x = 168,428,484/7,916
6. Step 6: Final answer
   x = 21,276.97