Finding the Fourth Proportional to 2,103.72, 3,155.63 and 642.88

Step by Step Solution

1. Step 1: Write the proportion equation
   2,103.72 : 3,155.63 = 642.88 : x
2. Step 2: Convert to fraction form
   2,103.72/3,155.63 = 642.88/x
3. Step 3: Cross multiply
   2,103.72x = 3,155.63 × 642.88
4. Step 4: Simplify right side
   2,103.72x = 2,028,691.41
5. Step 5: Solve for x
   x = 2,028,691.41/2,103.72
6. Step 6: Final answer
   x = 964.34