Finding the Third Proportional to 485.78 and 772.56

Step by Step Solution

1. Step 1: Write the proportion equation
   485.78 : 772.56 = 772.56 : x
2. Step 2: Convert to fraction form
   485.78/772.56 = 772.56/x
3. Step 3: Cross multiply
   485.78x = 772.56 × 772.56
4. Step 4: Simplify right side
   485.78x = 596,852.82
5. Step 5: Solve for x
   x = 596,852.82/485.78
6. Step 6: Final answer
   x = 1,228.65