Finding the Fourth Proportional to 12,639.78, 18,951.54 and 5,249.34

Step by Step Solution

1. Step 1: Write the proportion equation
   12,639.78 : 18,951.54 = 5,249.34 : x
2. Step 2: Convert to fraction form
   12,639.78/18,951.54 = 5,249.34/x
3. Step 3: Cross multiply
   12,639.78x = 18,951.54 × 5,249.34
4. Step 4: Simplify right side
   12,639.78x = 99,483,076.98
5. Step 5: Solve for x
   x = 99,483,076.98/12,639.78
6. Step 6: Final answer
   x = 7,870.63