Finding the Fourth Proportional to 28,442.16, 42,643.15 and 12,638.61

Step by Step Solution

1. Step 1: Write the proportion equation
   28,442.16 : 42,643.15 = 12,638.61 : x
2. Step 2: Convert to fraction form
   28,442.16/42,643.15 = 12,638.61/x
3. Step 3: Cross multiply
   28,442.16x = 42,643.15 × 12,638.61
4. Step 4: Simplify right side
   28,442.16x = 538,950,142.02
5. Step 5: Solve for x
   x = 538,950,142.02/28,442.16
6. Step 6: Final answer
   x = 18,948.99