Finding the Fourth Proportional to 42,721.43, 64,083.15 and 13,139.53

Step by Step Solution

1. Step 1: Write the proportion equation
   42,721.43 : 64,083.15 = 13,139.53 : x
2. Step 2: Convert to fraction form
   42,721.43/64,083.15 = 13,139.53/x
3. Step 3: Cross multiply
   42,721.43x = 64,083.15 × 13,139.53
4. Step 4: Simplify right side
   42,721.43x = 842,022,311.71
5. Step 5: Solve for x
   x = 842,022,311.71/42,721.43
6. Step 6: Final answer
   x = 19,709.60