Finding the Fourth Proportional to 21,279.30, 31,921.14 and 8,142.72

Step by Step Solution

1. Step 1: Write the proportion equation
   21,279.30 : 31,921.14 = 8,142.72 : x
2. Step 2: Convert to fraction form
   21,279.30/31,921.14 = 8,142.72/x
3. Step 3: Cross multiply
   21,279.30x = 31,921.14 × 8,142.72
4. Step 4: Simplify right side
   21,279.30x = 259,924,905.10
5. Step 5: Solve for x
   x = 259,924,905.10/21,279.30
6. Step 6: Final answer
   x = 12,214.92