Finding the Third Proportional to 128,140.50 and 280,419

Step by Step Solution

1. Step 1: Write the proportion equation
   128,140.50 : 280,419 = 280,419 : x
2. Step 2: Convert to fraction form
   128,140.50/280,419 = 280,419/x
3. Step 3: Cross multiply
   128,140.50x = 280,419 × 280,419
4. Step 4: Simplify right side
   128,140.50x = 78,634,815,561
5. Step 5: Solve for x
   x = 78,634,815,561/128,140.50
6. Step 6: Final answer
   x = 613,660.91