Finding the Fourth Proportional to 21,821.49, 30,115.89 and 12,871.89

Step by Step Solution

1. Step 1: Write the proportion equation
   21,821.49 : 30,115.89 = 12,871.89 : x
2. Step 2: Convert to fraction form
   21,821.49/30,115.89 = 12,871.89/x
3. Step 3: Cross multiply
   21,821.49x = 30,115.89 × 12,871.89
4. Step 4: Simplify right side
   21,821.49x = 387,648,423.33
5. Step 5: Solve for x
   x = 387,648,423.33/21,821.49
6. Step 6: Final answer
   x = 17,764.53