Finding the Fourth Proportional to 2,105.87, 3,158.55 and 644.90

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.87 : 3,158.55 = 644.90 : x
2. Step 2: Convert to fraction form
   2,105.87/3,158.55 = 644.90/x
3. Step 3: Cross multiply
   2,105.87x = 3,158.55 × 644.90
4. Step 4: Simplify right side
   2,105.87x = 2,036,933.10
5. Step 5: Solve for x
   x = 2,036,933.10/2,105.87
6. Step 6: Final answer
   x = 967.27