Finding the Fourth Proportional to 20,785.28, 31,142.72 and 12,560

Step by Step Solution

1. Step 1: Write the proportion equation
   20,785.28 : 31,142.72 = 12,560 : x
2. Step 2: Convert to fraction form
   20,785.28/31,142.72 = 12,560/x
3. Step 3: Cross multiply
   20,785.28x = 31,142.72 × 12,560
4. Step 4: Simplify right side
   20,785.28x = 391,152,563.20
5. Step 5: Solve for x
   x = 391,152,563.20/20,785.28
6. Step 6: Final answer
   x = 18,818.73