Finding the Fourth Proportional to 21,861.33, 30,171.20 and 12,431.31

Step by Step Solution

1. Step 1: Write the proportion equation
   21,861.33 : 30,171.20 = 12,431.31 : x
2. Step 2: Convert to fraction form
   21,861.33/30,171.20 = 12,431.31/x
3. Step 3: Cross multiply
   21,861.33x = 30,171.20 × 12,431.31
4. Step 4: Simplify right side
   21,861.33x = 375,067,540.27
5. Step 5: Solve for x
   x = 375,067,540.27/21,861.33
6. Step 6: Final answer
   x = 17,156.67