Finding the Fourth Proportional to 31,002.12, 42,789.72 and 20,392.80

Step by Step Solution

1. Step 1: Write the proportion equation
   31,002.12 : 42,789.72 = 20,392.80 : x
2. Step 2: Convert to fraction form
   31,002.12/42,789.72 = 20,392.80/x
3. Step 3: Cross multiply
   31,002.12x = 42,789.72 × 20,392.80
4. Step 4: Simplify right side
   31,002.12x = 872,602,202.02
5. Step 5: Solve for x
   x = 872,602,202.02/31,002.12
6. Step 6: Final answer
   x = 28,146.53