Finding the Fourth Proportional to 21,140.71, 31,715.51 and 7,992.79

Step by Step Solution

1. Step 1: Write the proportion equation
   21,140.71 : 31,715.51 = 7,992.79 : x
2. Step 2: Convert to fraction form
   21,140.71/31,715.51 = 7,992.79/x
3. Step 3: Cross multiply
   21,140.71x = 31,715.51 × 7,992.79
4. Step 4: Simplify right side
   21,140.71x = 253,495,411.17
5. Step 5: Solve for x
   x = 253,495,411.17/21,140.71
6. Step 6: Final answer
   x = 11,990.87