Finding the Fourth Proportional to 21,261.72, 29,340.72 and 12,309.60

Step by Step Solution

1. Step 1: Write the proportion equation
   21,261.72 : 29,340.72 = 12,309.60 : x
2. Step 2: Convert to fraction form
   21,261.72/29,340.72 = 12,309.60/x
3. Step 3: Cross multiply
   21,261.72x = 29,340.72 × 12,309.60
4. Step 4: Simplify right side
   21,261.72x = 361,172,526.91
5. Step 5: Solve for x
   x = 361,172,526.91/21,261.72
6. Step 6: Final answer
   x = 16,986.99