Finding the Fourth Proportional to 21,139.96, 31,707.20 and 7,990.62

Step by Step Solution

1. Step 1: Write the proportion equation
   21,139.96 : 31,707.20 = 7,990.62 : x
2. Step 2: Convert to fraction form
   21,139.96/31,707.20 = 7,990.62/x
3. Step 3: Cross multiply
   21,139.96x = 31,707.20 × 7,990.62
4. Step 4: Simplify right side
   21,139.96x = 253,360,186.46
5. Step 5: Solve for x
   x = 253,360,186.46/21,139.96
6. Step 6: Final answer
   x = 11,984.89