Finding the Fourth Proportional to 13,131.61, 18,121.62 and 8,415.89

Step by Step Solution

1. Step 1: Write the proportion equation
   13,131.61 : 18,121.62 = 8,415.89 : x
2. Step 2: Convert to fraction form
   13,131.61/18,121.62 = 8,415.89/x
3. Step 3: Cross multiply
   13,131.61x = 18,121.62 × 8,415.89
4. Step 4: Simplify right side
   13,131.61x = 152,509,605.85
5. Step 5: Solve for x
   x = 152,509,605.85/13,131.61
6. Step 6: Final answer
   x = 11,613.93