Finding the Fourth Proportional to 21,081.16, 31,617.64 and 7,929.09

Step by Step Solution

1. Step 1: Write the proportion equation
   21,081.16 : 31,617.64 = 7,929.09 : x
2. Step 2: Convert to fraction form
   21,081.16/31,617.64 = 7,929.09/x
3. Step 3: Cross multiply
   21,081.16x = 31,617.64 × 7,929.09
4. Step 4: Simplify right side
   21,081.16x = 250,699,123.06
5. Step 5: Solve for x
   x = 250,699,123.06/21,081.16
6. Step 6: Final answer
   x = 11,892.09