Finding the Fourth Proportional to 21,018.47, 28,996.29 and 13,839.12

Step by Step Solution

1. Step 1: Write the proportion equation
   21,018.47 : 28,996.29 = 13,839.12 : x
2. Step 2: Convert to fraction form
   21,018.47/28,996.29 = 13,839.12/x
3. Step 3: Cross multiply
   21,018.47x = 28,996.29 × 13,839.12
4. Step 4: Simplify right side
   21,018.47x = 401,283,136.86
5. Step 5: Solve for x
   x = 401,283,136.86/21,018.47
6. Step 6: Final answer
   x = 19,091.93