Finding the Fourth Proportional to 28,139.61, 42,215.49 and 8,419.89

Step by Step Solution

1. Step 1: Write the proportion equation
   28,139.61 : 42,215.49 = 8,419.89 : x
2. Step 2: Convert to fraction form
   28,139.61/42,215.49 = 8,419.89/x
3. Step 3: Cross multiply
   28,139.61x = 42,215.49 × 8,419.89
4. Step 4: Simplify right side
   28,139.61x = 355,449,782.10
5. Step 5: Solve for x
   x = 355,449,782.10/28,139.61
6. Step 6: Final answer
   x = 12,631.65