Finding the Fourth Proportional to 5,411.02, 8,118.15 and 2,639.20

Step by Step Solution

1. Step 1: Write the proportion equation
   5,411.02 : 8,118.15 = 2,639.20 : x
2. Step 2: Convert to fraction form
   5,411.02/8,118.15 = 2,639.20/x
3. Step 3: Cross multiply
   5,411.02x = 8,118.15 × 2,639.20
4. Step 4: Simplify right side
   5,411.02x = 21,425,421.48
5. Step 5: Solve for x
   x = 21,425,421.48/5,411.02
6. Step 6: Final answer
   x = 3,959.59