Finding the Third Proportional to 309.56 and 699.56

Step by Step Solution

1. Step 1: Write the proportion equation
   309.56 : 699.56 = 699.56 : x
2. Step 2: Convert to fraction form
   309.56/699.56 = 699.56/x
3. Step 3: Cross multiply
   309.56x = 699.56 × 699.56
4. Step 4: Simplify right side
   309.56x = 489,387.69
5. Step 5: Solve for x
   x = 489,387.69/309.56
6. Step 6: Final answer
   x = 1,580.90