Finding the Fourth Proportional to 21,915.72, 30,245.81 and 12,966.10

Step by Step Solution

1. Step 1: Write the proportion equation
   21,915.72 : 30,245.81 = 12,966.10 : x
2. Step 2: Convert to fraction form
   21,915.72/30,245.81 = 12,966.10/x
3. Step 3: Cross multiply
   21,915.72x = 30,245.81 × 12,966.10
4. Step 4: Simplify right side
   21,915.72x = 392,170,197.04
5. Step 5: Solve for x
   x = 392,170,197.04/21,915.72
6. Step 6: Final answer
   x = 17,894.47