Finding the Fourth Proportional to 31,142.17, 42,983.20 and 20,380.80

Step by Step Solution

1. Step 1: Write the proportion equation
   31,142.17 : 42,983.20 = 20,380.80 : x
2. Step 2: Convert to fraction form
   31,142.17/42,983.20 = 20,380.80/x
3. Step 3: Cross multiply
   31,142.17x = 42,983.20 × 20,380.80
4. Step 4: Simplify right side
   31,142.17x = 876,031,890.12
5. Step 5: Solve for x
   x = 876,031,890.12/31,142.17
6. Step 6: Final answer
   x = 28,130.08