Finding the Fourth Proportional to 21,080, 29,086.90 and 12,585.57

Step by Step Solution

1. Step 1: Write the proportion equation
   21,080 : 29,086.90 = 12,585.57 : x
2. Step 2: Convert to fraction form
   21,080/29,086.90 = 12,585.57/x
3. Step 3: Cross multiply
   21,080x = 29,086.90 × 12,585.57
4. Step 4: Simplify right side
   21,080x = 366,075,007.67
5. Step 5: Solve for x
   x = 366,075,007.67/21,080
6. Step 6: Final answer
   x = 17,365.99