Finding the Fourth Proportional to 21,123.91, 29,145.81 and 12,945.28

Step by Step Solution

1. Step 1: Write the proportion equation
   21,123.91 : 29,145.81 = 12,945.28 : x
2. Step 2: Convert to fraction form
   21,123.91/29,145.81 = 12,945.28/x
3. Step 3: Cross multiply
   21,123.91x = 29,145.81 × 12,945.28
4. Step 4: Simplify right side
   21,123.91x = 377,300,671.28
5. Step 5: Solve for x
   x = 377,300,671.28/21,123.91
6. Step 6: Final answer
   x = 17,861.31