Finding the Fourth Proportional to 2,586.78, 3,880.89 and 856.62

Step by Step Solution

1. Step 1: Write the proportion equation
   2,586.78 : 3,880.89 = 856.62 : x
2. Step 2: Convert to fraction form
   2,586.78/3,880.89 = 856.62/x
3. Step 3: Cross multiply
   2,586.78x = 3,880.89 × 856.62
4. Step 4: Simplify right side
   2,586.78x = 3,324,447.99
5. Step 5: Solve for x
   x = 3,324,447.99/2,586.78
6. Step 6: Final answer
   x = 1,285.17