Finding the Third Proportional to 778.78 and 1,131.89

Step by Step Solution

1. Step 1: Write the proportion equation
   778.78 : 1,131.89 = 1,131.89 : x
2. Step 2: Convert to fraction form
   778.78/1,131.89 = 1,131.89/x
3. Step 3: Cross multiply
   778.78x = 1,131.89 × 1,131.89
4. Step 4: Simplify right side
   778.78x = 1,281,176.39
5. Step 5: Solve for x
   x = 1,281,176.39/778.78
6. Step 6: Final answer
   x = 1,645.10