Finding the Third Proportional to 639.88 and 1,393.56

Step by Step Solution

1. Step 1: Write the proportion equation
   639.88 : 1,393.56 = 1,393.56 : x
2. Step 2: Convert to fraction form
   639.88/1,393.56 = 1,393.56/x
3. Step 3: Cross multiply
   639.88x = 1,393.56 × 1,393.56
4. Step 4: Simplify right side
   639.88x = 1,942,016.44
5. Step 5: Solve for x
   x = 1,942,016.44/639.88
6. Step 6: Final answer
   x = 3,034.99