Finding the Fourth Proportional to 12,986.72, 17,921.42 and 7,321.40

Step by Step Solution

1. Step 1: Write the proportion equation
   12,986.72 : 17,921.42 = 7,321.40 : x
2. Step 2: Convert to fraction form
   12,986.72/17,921.42 = 7,321.40/x
3. Step 3: Cross multiply
   12,986.72x = 17,921.42 × 7,321.40
4. Step 4: Simplify right side
   12,986.72x = 131,209,884.39
5. Step 5: Solve for x
   x = 131,209,884.39/12,986.72
6. Step 6: Final answer
   x = 10,103.39