Finding the Fourth Proportional to 2,612.17, 3,919.10 and 857.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,612.17 : 3,919.10 = 857.20 : x
2. Step 2: Convert to fraction form
   2,612.17/3,919.10 = 857.20/x
3. Step 3: Cross multiply
   2,612.17x = 3,919.10 × 857.20
4. Step 4: Simplify right side
   2,612.17x = 3,359,452.52
5. Step 5: Solve for x
   x = 3,359,452.52/2,612.17
6. Step 6: Final answer
   x = 1,286.08