Finding the Fourth Proportional to 21,280.30, 31,922.64 and 8,143.72

Step by Step Solution

1. Step 1: Write the proportion equation
   21,280.30 : 31,922.64 = 8,143.72 : x
2. Step 2: Convert to fraction form
   21,280.30/31,922.64 = 8,143.72/x
3. Step 3: Cross multiply
   21,280.30x = 31,922.64 × 8,143.72
4. Step 4: Simplify right side
   21,280.30x = 259,969,041.82
5. Step 5: Solve for x
   x = 259,969,041.82/21,280.30
6. Step 6: Final answer
   x = 12,216.42