Finding the Fourth Proportional to 2,105.81, 3,158.87 and 644.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.81 : 3,158.87 = 644.78 : x
2. Step 2: Convert to fraction form
   2,105.81/3,158.87 = 644.78/x
3. Step 3: Cross multiply
   2,105.81x = 3,158.87 × 644.78
4. Step 4: Simplify right side
   2,105.81x = 2,036,757.18
5. Step 5: Solve for x
   x = 2,036,757.18/2,105.81
6. Step 6: Final answer
   x = 967.21