Finding the Fourth Proportional to 2,105.78, 3,159.14 and 645.05

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.78 : 3,159.14 = 645.05 : x
2. Step 2: Convert to fraction form
   2,105.78/3,159.14 = 645.05/x
3. Step 3: Cross multiply
   2,105.78x = 3,159.14 × 645.05
4. Step 4: Simplify right side
   2,105.78x = 2,037,807.93
5. Step 5: Solve for x
   x = 2,037,807.93/2,105.78
6. Step 6: Final answer
   x = 967.72