Finding the Fourth Proportional to 21,870.96, 30,179.88 and 12,439.20

Step by Step Solution

1. Step 1: Write the proportion equation
   21,870.96 : 30,179.88 = 12,439.20 : x
2. Step 2: Convert to fraction form
   21,870.96/30,179.88 = 12,439.20/x
3. Step 3: Cross multiply
   21,870.96x = 30,179.88 × 12,439.20
4. Step 4: Simplify right side
   21,870.96x = 375,413,563.30
5. Step 5: Solve for x
   x = 375,413,563.30/21,870.96
6. Step 6: Final answer
   x = 17,164.93