Finding the Fourth Proportional to 21,105.36, 29,131.17 and 13,142.88

Step by Step Solution

1. Step 1: Write the proportion equation
   21,105.36 : 29,131.17 = 13,142.88 : x
2. Step 2: Convert to fraction form
   21,105.36/29,131.17 = 13,142.88/x
3. Step 3: Cross multiply
   21,105.36x = 29,131.17 × 13,142.88
4. Step 4: Simplify right side
   21,105.36x = 382,867,471.57
5. Step 5: Solve for x
   x = 382,867,471.57/21,105.36
6. Step 6: Final answer
   x = 18,140.77