Finding the Fourth Proportional to 9,111.30, 12,729.90 and 9,111.30

Step by Step Solution

1. Step 1: Write the proportion equation
   9,111.30 : 12,729.90 = 9,111.30 : x
2. Step 2: Convert to fraction form
   9,111.30/12,729.90 = 9,111.30/x
3. Step 3: Cross multiply
   9,111.30x = 12,729.90 × 9,111.30
4. Step 4: Simplify right side
   9,111.30x = 115,985,937.87
5. Step 5: Solve for x
   x = 115,985,937.87/9,111.30
6. Step 6: Final answer
   x = 12,729.90