Finding the Fourth Proportional to 8,642, 12,891.16 and 8,499.31

Step by Step Solution

1. Step 1: Write the proportion equation
   8,642 : 12,891.16 = 8,499.31 : x
2. Step 2: Convert to fraction form
   8,642/12,891.16 = 8,499.31/x
3. Step 3: Cross multiply
   8,642x = 12,891.16 × 8,499.31
4. Step 4: Simplify right side
   8,642x = 109,565,965.10
5. Step 5: Solve for x
   x = 109,565,965.10/8,642
6. Step 6: Final answer
   x = 12,678.31