Finding the Third Proportional to 128.75 and 280.25

Step by Step Solution

1. Step 1: Write the proportion equation
   128.75 : 280.25 = 280.25 : x
2. Step 2: Convert to fraction form
   128.75/280.25 = 280.25/x
3. Step 3: Cross multiply
   128.75x = 280.25 × 280.25
4. Step 4: Simplify right side
   128.75x = 78,540.06
5. Step 5: Solve for x
   x = 78,540.06/128.75
6. Step 6: Final answer
   x = 610.02