Finding the Fourth Proportional to 2,105.18, 3,156.88 and 644

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.18 : 3,156.88 = 644 : x
2. Step 2: Convert to fraction form
   2,105.18/3,156.88 = 644/x
3. Step 3: Cross multiply
   2,105.18x = 3,156.88 × 644
4. Step 4: Simplify right side
   2,105.18x = 2,033,030.72
5. Step 5: Solve for x
   x = 2,033,030.72/2,105.18
6. Step 6: Final answer
   x = 965.73