Finding the Fourth Proportional to 12,399.87, 17,111.21 and 7,021.47

Step by Step Solution

1. Step 1: Write the proportion equation
   12,399.87 : 17,111.21 = 7,021.47 : x
2. Step 2: Convert to fraction form
   12,399.87/17,111.21 = 7,021.47/x
3. Step 3: Cross multiply
   12,399.87x = 17,111.21 × 7,021.47
4. Step 4: Simplify right side
   12,399.87x = 120,145,812.57
5. Step 5: Solve for x
   x = 120,145,812.57/12,399.87
6. Step 6: Final answer
   x = 9,689.28