Finding the Fourth Proportional to 21,142.10, 31,720.50 and 13,235.55

Step by Step Solution

1. Step 1: Write the proportion equation
   21,142.10 : 31,720.50 = 13,235.55 : x
2. Step 2: Convert to fraction form
   21,142.10/31,720.50 = 13,235.55/x
3. Step 3: Cross multiply
   21,142.10x = 31,720.50 × 13,235.55
4. Step 4: Simplify right side
   21,142.10x = 419,838,263.78
5. Step 5: Solve for x
   x = 419,838,263.78/21,142.10
6. Step 6: Final answer
   x = 19,857.93