Finding the Fourth Proportional to 2,808.69, 4,213.17 and 861.05

Step by Step Solution

1. Step 1: Write the proportion equation
   2,808.69 : 4,213.17 = 861.05 : x
2. Step 2: Convert to fraction form
   2,808.69/4,213.17 = 861.05/x
3. Step 3: Cross multiply
   2,808.69x = 4,213.17 × 861.05
4. Step 4: Simplify right side
   2,808.69x = 3,627,728.96
5. Step 5: Solve for x
   x = 3,627,728.96/2,808.69
6. Step 6: Final answer
   x = 1,291.61