Finding the Fourth Proportional to 13,680.72, 18,879.12 and 7,712.28

Step by Step Solution

1. Step 1: Write the proportion equation
   13,680.72 : 18,879.12 = 7,712.28 : x
2. Step 2: Convert to fraction form
   13,680.72/18,879.12 = 7,712.28/x
3. Step 3: Cross multiply
   13,680.72x = 18,879.12 × 7,712.28
4. Step 4: Simplify right side
   13,680.72x = 145,601,059.59
5. Step 5: Solve for x
   x = 145,601,059.59/13,680.72
6. Step 6: Final answer
   x = 10,642.79