Finding the Fourth Proportional to 8,178.78, 12,238.89 and 6,429.18

Step by Step Solution

1. Step 1: Write the proportion equation
   8,178.78 : 12,238.89 = 6,429.18 : x
2. Step 2: Convert to fraction form
   8,178.78/12,238.89 = 6,429.18/x
3. Step 3: Cross multiply
   8,178.78x = 12,238.89 × 6,429.18
4. Step 4: Simplify right side
   8,178.78x = 78,686,026.81
5. Step 5: Solve for x
   x = 78,686,026.81/8,178.78
6. Step 6: Final answer
   x = 9,620.75