Finding the Fourth Proportional to 21,304.02, 31,920.72 and 12,958.80

Step by Step Solution

1. Step 1: Write the proportion equation
   21,304.02 : 31,920.72 = 12,958.80 : x
2. Step 2: Convert to fraction form
   21,304.02/31,920.72 = 12,958.80/x
3. Step 3: Cross multiply
   21,304.02x = 31,920.72 × 12,958.80
4. Step 4: Simplify right side
   21,304.02x = 413,654,226.34
5. Step 5: Solve for x
   x = 413,654,226.34/21,304.02
6. Step 6: Final answer
   x = 19,416.72