Finding the Fourth Proportional to 13,667.78, 18,872.71 and 8,640.11

Step by Step Solution

1. Step 1: Write the proportion equation
   13,667.78 : 18,872.71 = 8,640.11 : x
2. Step 2: Convert to fraction form
   13,667.78/18,872.71 = 8,640.11/x
3. Step 3: Cross multiply
   13,667.78x = 18,872.71 × 8,640.11
4. Step 4: Simplify right side
   13,667.78x = 163,062,174.43
5. Step 5: Solve for x
   x = 163,062,174.43/13,667.78
6. Step 6: Final answer
   x = 11,930.41