Finding the Fourth Proportional to 9,412.78, 12,989.31 and 5,221.42

Step by Step Solution

1. Step 1: Write the proportion equation
   9,412.78 : 12,989.31 = 5,221.42 : x
2. Step 2: Convert to fraction form
   9,412.78/12,989.31 = 5,221.42/x
3. Step 3: Cross multiply
   9,412.78x = 12,989.31 × 5,221.42
4. Step 4: Simplify right side
   9,412.78x = 67,822,643.02
5. Step 5: Solve for x
   x = 67,822,643.02/9,412.78
6. Step 6: Final answer
   x = 7,205.38