Finding the Fourth Proportional to 12,686.64, 17,501.61 and 8,439.78

Step by Step Solution

1. Step 1: Write the proportion equation
   12,686.64 : 17,501.61 = 8,439.78 : x
2. Step 2: Convert to fraction form
   12,686.64/17,501.61 = 8,439.78/x
3. Step 3: Cross multiply
   12,686.64x = 17,501.61 × 8,439.78
4. Step 4: Simplify right side
   12,686.64x = 147,709,738.05
5. Step 5: Solve for x
   x = 147,709,738.05/12,686.64
6. Step 6: Final answer
   x = 11,642.94