Finding the Fourth Proportional to 2,158.56, 3,238.38 and 860.40

Step by Step Solution

1. Step 1: Write the proportion equation
   2,158.56 : 3,238.38 = 860.40 : x
2. Step 2: Convert to fraction form
   2,158.56/3,238.38 = 860.40/x
3. Step 3: Cross multiply
   2,158.56x = 3,238.38 × 860.40
4. Step 4: Simplify right side
   2,158.56x = 2,786,302.15
5. Step 5: Solve for x
   x = 2,786,302.15/2,158.56
6. Step 6: Final answer
   x = 1,290.82