Finding the Fourth Proportional to 21,816.72, 30,085.48 and 13,431.60

Step by Step Solution

1. Step 1: Write the proportion equation
   21,816.72 : 30,085.48 = 13,431.60 : x
2. Step 2: Convert to fraction form
   21,816.72/30,085.48 = 13,431.60/x
3. Step 3: Cross multiply
   21,816.72x = 30,085.48 × 13,431.60
4. Step 4: Simplify right side
   21,816.72x = 404,096,133.17
5. Step 5: Solve for x
   x = 404,096,133.17/21,816.72
6. Step 6: Final answer
   x = 18,522.31