Finding the Fourth Proportional to 13,128.65, 18,114.32 and 8,419.31

Step by Step Solution

1. Step 1: Write the proportion equation
   13,128.65 : 18,114.32 = 8,419.31 : x
2. Step 2: Convert to fraction form
   13,128.65/18,114.32 = 8,419.31/x
3. Step 3: Cross multiply
   13,128.65x = 18,114.32 × 8,419.31
4. Step 4: Simplify right side
   13,128.65x = 152,509,942.85
5. Step 5: Solve for x
   x = 152,509,942.85/13,128.65
6. Step 6: Final answer
   x = 11,616.58