Finding the Fourth Proportional to 21,643.28, 29,859.50 and 13,142.18

Step by Step Solution

1. Step 1: Write the proportion equation
   21,643.28 : 29,859.50 = 13,142.18 : x
2. Step 2: Convert to fraction form
   21,643.28/29,859.50 = 13,142.18/x
3. Step 3: Cross multiply
   21,643.28x = 29,859.50 × 13,142.18
4. Step 4: Simplify right side
   21,643.28x = 392,418,887.90
5. Step 5: Solve for x
   x = 392,418,887.90/21,643.28
6. Step 6: Final answer
   x = 18,131.21