Finding the Third Proportional to 778.50 and 1,687.78

Step by Step Solution

1. Step 1: Write the proportion equation
   778.50 : 1,687.78 = 1,687.78 : x
2. Step 2: Convert to fraction form
   778.50/1,687.78 = 1,687.78/x
3. Step 3: Cross multiply
   778.50x = 1,687.78 × 1,687.78
4. Step 4: Simplify right side
   778.50x = 2,848,605.55
5. Step 5: Solve for x
   x = 2,848,605.55/778.50
6. Step 6: Final answer
   x = 3,659.10