Finding the Fourth Proportional to 21,808.17, 30,099.20 and 12,855.15

Step by Step Solution

1. Step 1: Write the proportion equation
   21,808.17 : 30,099.20 = 12,855.15 : x
2. Step 2: Convert to fraction form
   21,808.17/30,099.20 = 12,855.15/x
3. Step 3: Cross multiply
   21,808.17x = 30,099.20 × 12,855.15
4. Step 4: Simplify right side
   21,808.17x = 386,929,730.88
5. Step 5: Solve for x
   x = 386,929,730.88/21,808.17
6. Step 6: Final answer
   x = 17,742.42