Finding the Third Proportional to 679.78 and 814.78

Step by Step Solution

1. Step 1: Write the proportion equation
   679.78 : 814.78 = 814.78 : x
2. Step 2: Convert to fraction form
   679.78/814.78 = 814.78/x
3. Step 3: Cross multiply
   679.78x = 814.78 × 814.78
4. Step 4: Simplify right side
   679.78x = 663,868.49
5. Step 5: Solve for x
   x = 663,868.49/679.78
6. Step 6: Final answer
   x = 976.59