Finding the Fourth Proportional to 21,229.74, 31,809.72 and 12,912.15

Step by Step Solution

1. Step 1: Write the proportion equation
   21,229.74 : 31,809.72 = 12,912.15 : x
2. Step 2: Convert to fraction form
   21,229.74/31,809.72 = 12,912.15/x
3. Step 3: Cross multiply
   21,229.74x = 31,809.72 × 12,912.15
4. Step 4: Simplify right side
   21,229.74x = 410,731,876.10
5. Step 5: Solve for x
   x = 410,731,876.10/21,229.74
6. Step 6: Final answer
   x = 19,347.00