Finding the Fourth Proportional to 21,028.20, 31,499.10 and 10,645.80

Step by Step Solution

1. Step 1: Write the proportion equation
   21,028.20 : 31,499.10 = 10,645.80 : x
2. Step 2: Convert to fraction form
   21,028.20/31,499.10 = 10,645.80/x
3. Step 3: Cross multiply
   21,028.20x = 31,499.10 × 10,645.80
4. Step 4: Simplify right side
   21,028.20x = 335,333,118.78
5. Step 5: Solve for x
   x = 335,333,118.78/21,028.20
6. Step 6: Final answer
   x = 15,946.83