Finding the Fourth Proportional to 12,890.88, 17,779.37 and 8,640.54

Step by Step Solution

1. Step 1: Write the proportion equation
   12,890.88 : 17,779.37 = 8,640.54 : x
2. Step 2: Convert to fraction form
   12,890.88/17,779.37 = 8,640.54/x
3. Step 3: Cross multiply
   12,890.88x = 17,779.37 × 8,640.54
4. Step 4: Simplify right side
   12,890.88x = 153,623,314.46
5. Step 5: Solve for x
   x = 153,623,314.46/12,890.88
6. Step 6: Final answer
   x = 11,917.21