Finding the Third Proportional to 128,860.50 and 261,345

Step by Step Solution

1. Step 1: Write the proportion equation
   128,860.50 : 261,345 = 261,345 : x
2. Step 2: Convert to fraction form
   128,860.50/261,345 = 261,345/x
3. Step 3: Cross multiply
   128,860.50x = 261,345 × 261,345
4. Step 4: Simplify right side
   128,860.50x = 68,301,209,025
5. Step 5: Solve for x
   x = 68,301,209,025/128,860.50
6. Step 6: Final answer
   x = 530,039.92