Finding the Fourth Proportional to 2,105.17, 3,158.10 and 644.20

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.17 : 3,158.10 = 644.20 : x
2. Step 2: Convert to fraction form
   2,105.17/3,158.10 = 644.20/x
3. Step 3: Cross multiply
   2,105.17x = 3,158.10 × 644.20
4. Step 4: Simplify right side
   2,105.17x = 2,034,448.02
5. Step 5: Solve for x
   x = 2,034,448.02/2,105.17
6. Step 6: Final answer
   x = 966.41