Finding the Fourth Proportional to 2,178.64, 3,265.71 and 861.86

Step by Step Solution

1. Step 1: Write the proportion equation
   2,178.64 : 3,265.71 = 861.86 : x
2. Step 2: Convert to fraction form
   2,178.64/3,265.71 = 861.86/x
3. Step 3: Cross multiply
   2,178.64x = 3,265.71 × 861.86
4. Step 4: Simplify right side
   2,178.64x = 2,814,584.82
5. Step 5: Solve for x
   x = 2,814,584.82/2,178.64
6. Step 6: Final answer
   x = 1,291.90