Finding the Fourth Proportional to 9,131.20, 12,809.60 and 9,131.20

Step by Step Solution

1. Step 1: Write the proportion equation
   9,131.20 : 12,809.60 = 9,131.20 : x
2. Step 2: Convert to fraction form
   9,131.20/12,809.60 = 9,131.20/x
3. Step 3: Cross multiply
   9,131.20x = 12,809.60 × 9,131.20
4. Step 4: Simplify right side
   9,131.20x = 116,967,019.52
5. Step 5: Solve for x
   x = 116,967,019.52/9,131.20
6. Step 6: Final answer
   x = 12,809.60