Finding the Fourth Proportional to 28,105.60, 42,165.20 and 8,385.72

Step by Step Solution

1. Step 1: Write the proportion equation
   28,105.60 : 42,165.20 = 8,385.72 : x
2. Step 2: Convert to fraction form
   28,105.60/42,165.20 = 8,385.72/x
3. Step 3: Cross multiply
   28,105.60x = 42,165.20 × 8,385.72
4. Step 4: Simplify right side
   28,105.60x = 353,585,560.94
5. Step 5: Solve for x
   x = 353,585,560.94/28,105.60
6. Step 6: Final answer
   x = 12,580.61