Finding the Fourth Proportional to 11,151.78, 15,376.77 and 9,128.76

Step by Step Solution

1. Step 1: Write the proportion equation
   11,151.78 : 15,376.77 = 9,128.76 : x
2. Step 2: Convert to fraction form
   11,151.78/15,376.77 = 9,128.76/x
3. Step 3: Cross multiply
   11,151.78x = 15,376.77 × 9,128.76
4. Step 4: Simplify right side
   11,151.78x = 140,370,842.91
5. Step 5: Solve for x
   x = 140,370,842.91/11,151.78
6. Step 6: Final answer
   x = 12,587.30