Finding the Fourth Proportional to 21,005.40, 28,979.82 and 12,510.12

Step by Step Solution

1. Step 1: Write the proportion equation
   21,005.40 : 28,979.82 = 12,510.12 : x
2. Step 2: Convert to fraction form
   21,005.40/28,979.82 = 12,510.12/x
3. Step 3: Cross multiply
   21,005.40x = 28,979.82 × 12,510.12
4. Step 4: Simplify right side
   21,005.40x = 362,541,025.78
5. Step 5: Solve for x
   x = 362,541,025.78/21,005.40
6. Step 6: Final answer
   x = 17,259.42