Finding the Fourth Proportional to 21,278.96, 31,920.55 and 8,142.38

Step by Step Solution

1. Step 1: Write the proportion equation
   21,278.96 : 31,920.55 = 8,142.38 : x
2. Step 2: Convert to fraction form
   21,278.96/31,920.55 = 8,142.38/x
3. Step 3: Cross multiply
   21,278.96x = 31,920.55 × 8,142.38
4. Step 4: Simplify right side
   21,278.96x = 259,909,088.31
5. Step 5: Solve for x
   x = 259,909,088.31/21,278.96
6. Step 6: Final answer
   x = 12,214.37