Finding the Fourth Proportional to 2,105.73, 3,158.77 and 645.91

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.73 : 3,158.77 = 645.91 : x
2. Step 2: Convert to fraction form
   2,105.73/3,158.77 = 645.91/x
3. Step 3: Cross multiply
   2,105.73x = 3,158.77 × 645.91
4. Step 4: Simplify right side
   2,105.73x = 2,040,281.13
5. Step 5: Solve for x
   x = 2,040,281.13/2,105.73
6. Step 6: Final answer
   x = 968.92