Finding the Fourth Proportional to 8,128.79, 11,216.21 and 5,142.53

Step by Step Solution

1. Step 1: Write the proportion equation
   8,128.79 : 11,216.21 = 5,142.53 : x
2. Step 2: Convert to fraction form
   8,128.79/11,216.21 = 5,142.53/x
3. Step 3: Cross multiply
   8,128.79x = 11,216.21 × 5,142.53
4. Step 4: Simplify right side
   8,128.79x = 57,679,664.57
5. Step 5: Solve for x
   x = 57,679,664.57/8,128.79
6. Step 6: Final answer
   x = 7,095.72