Finding the Fourth Proportional to 15,789.29, 21,789.40 and 8,715.72

Step by Step Solution

1. Step 1: Write the proportion equation
   15,789.29 : 21,789.40 = 8,715.72 : x
2. Step 2: Convert to fraction form
   15,789.29/21,789.40 = 8,715.72/x
3. Step 3: Cross multiply
   15,789.29x = 21,789.40 × 8,715.72
4. Step 4: Simplify right side
   15,789.29x = 189,910,200.42
5. Step 5: Solve for x
   x = 189,910,200.42/15,789.29
6. Step 6: Final answer
   x = 12,027.79