Finding the Fourth Proportional to 12,915.87, 17,819.31 and 8,442.20

Step by Step Solution

1. Step 1: Write the proportion equation
   12,915.87 : 17,819.31 = 8,442.20 : x
2. Step 2: Convert to fraction form
   12,915.87/17,819.31 = 8,442.20/x
3. Step 3: Cross multiply
   12,915.87x = 17,819.31 × 8,442.20
4. Step 4: Simplify right side
   12,915.87x = 150,434,178.88
5. Step 5: Solve for x
   x = 150,434,178.88/12,915.87
6. Step 6: Final answer
   x = 11,647.24