Finding the Third Proportional to 3,128.25 and 7,128.75

Step by Step Solution

1. Step 1: Write the proportion equation
   3,128.25 : 7,128.75 = 7,128.75 : x
2. Step 2: Convert to fraction form
   3,128.25/7,128.75 = 7,128.75/x
3. Step 3: Cross multiply
   3,128.25x = 7,128.75 × 7,128.75
4. Step 4: Simplify right side
   3,128.25x = 50,819,076.56
5. Step 5: Solve for x
   x = 50,819,076.56/3,128.25
6. Step 6: Final answer
   x = 16,245.21