Finding the Third Proportional to 310.78 and 680.27

Step by Step Solution

1. Step 1: Write the proportion equation
   310.78 : 680.27 = 680.27 : x
2. Step 2: Convert to fraction form
   310.78/680.27 = 680.27/x
3. Step 3: Cross multiply
   310.78x = 680.27 × 680.27
4. Step 4: Simplify right side
   310.78x = 462,771.95
5. Step 5: Solve for x
   x = 462,771.95/310.78
6. Step 6: Final answer
   x = 1,489.06