Finding the Fourth Proportional to 13,789.72, 20,681.47 and 3,928.78

Step by Step Solution

1. Step 1: Write the proportion equation
   13,789.72 : 20,681.47 = 3,928.78 : x
2. Step 2: Convert to fraction form
   13,789.72/20,681.47 = 3,928.78/x
3. Step 3: Cross multiply
   13,789.72x = 20,681.47 × 3,928.78
4. Step 4: Simplify right side
   13,789.72x = 81,252,945.71
5. Step 5: Solve for x
   x = 81,252,945.71/13,789.72
6. Step 6: Final answer
   x = 5,892.28