Finding the Fourth Proportional to 21,178.72, 31,764.30 and 12,404.80

Step by Step Solution

1. Step 1: Write the proportion equation
   21,178.72 : 31,764.30 = 12,404.80 : x
2. Step 2: Convert to fraction form
   21,178.72/31,764.30 = 12,404.80/x
3. Step 3: Cross multiply
   21,178.72x = 31,764.30 × 12,404.80
4. Step 4: Simplify right side
   21,178.72x = 394,029,788.64
5. Step 5: Solve for x
   x = 394,029,788.64/21,178.72
6. Step 6: Final answer
   x = 18,604.99