Finding the Fourth Proportional to 21,816.14, 30,105.60 and 12,864.20

Step by Step Solution

1. Step 1: Write the proportion equation
   21,816.14 : 30,105.60 = 12,864.20 : x
2. Step 2: Convert to fraction form
   21,816.14/30,105.60 = 12,864.20/x
3. Step 3: Cross multiply
   21,816.14x = 30,105.60 × 12,864.20
4. Step 4: Simplify right side
   21,816.14x = 387,284,459.52
5. Step 5: Solve for x
   x = 387,284,459.52/21,816.14
6. Step 6: Final answer
   x = 17,752.20