Finding the Fourth Proportional to 10,689.90, 16,032.42 and 5,139.78

Step by Step Solution

1. Step 1: Write the proportion equation
   10,689.90 : 16,032.42 = 5,139.78 : x
2. Step 2: Convert to fraction form
   10,689.90/16,032.42 = 5,139.78/x
3. Step 3: Cross multiply
   10,689.90x = 16,032.42 × 5,139.78
4. Step 4: Simplify right side
   10,689.90x = 82,403,111.67
5. Step 5: Solve for x
   x = 82,403,111.67/10,689.90
6. Step 6: Final answer
   x = 7,708.50