Finding the Fourth Proportional to 12,390.72, 17,107.20 and 7,680

Step by Step Solution

1. Step 1: Write the proportion equation
   12,390.72 : 17,107.20 = 7,680 : x
2. Step 2: Convert to fraction form
   12,390.72/17,107.20 = 7,680/x
3. Step 3: Cross multiply
   12,390.72x = 17,107.20 × 7,680
4. Step 4: Simplify right side
   12,390.72x = 131,383,296
5. Step 5: Solve for x
   x = 131,383,296/12,390.72
6. Step 6: Final answer
   x = 10,603.36