Finding the Fourth Proportional to 28,013.04, 42,013.68 and 12,420.72

Step by Step Solution

1. Step 1: Write the proportion equation
   28,013.04 : 42,013.68 = 12,420.72 : x
2. Step 2: Convert to fraction form
   28,013.04/42,013.68 = 12,420.72/x
3. Step 3: Cross multiply
   28,013.04x = 42,013.68 × 12,420.72
4. Step 4: Simplify right side
   28,013.04x = 521,840,155.45
5. Step 5: Solve for x
   x = 521,840,155.45/28,013.04
6. Step 6: Final answer
   x = 18,628.47