Finding the Fourth Proportional to 2,103.62, 3,155.49 and 642.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,103.62 : 3,155.49 = 642.78 : x
2. Step 2: Convert to fraction form
   2,103.62/3,155.49 = 642.78/x
3. Step 3: Cross multiply
   2,103.62x = 3,155.49 × 642.78
4. Step 4: Simplify right side
   2,103.62x = 2,028,285.86
5. Step 5: Solve for x
   x = 2,028,285.86/2,103.62
6. Step 6: Final answer
   x = 964.19