Finding the Fourth Proportional to 21,047.76, 31,561.92 and 7,890.72

Step by Step Solution

1. Step 1: Write the proportion equation
   21,047.76 : 31,561.92 = 7,890.72 : x
2. Step 2: Convert to fraction form
   21,047.76/31,561.92 = 7,890.72/x
3. Step 3: Cross multiply
   21,047.76x = 31,561.92 × 7,890.72
4. Step 4: Simplify right side
   21,047.76x = 249,046,273.38
5. Step 5: Solve for x
   x = 249,046,273.38/21,047.76
6. Step 6: Final answer
   x = 11,832.44