Finding the Fourth Proportional to 2,590.56, 3,885.82 and 642.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,590.56 : 3,885.82 = 642.78 : x
2. Step 2: Convert to fraction form
   2,590.56/3,885.82 = 642.78/x
3. Step 3: Cross multiply
   2,590.56x = 3,885.82 × 642.78
4. Step 4: Simplify right side
   2,590.56x = 2,497,727.38
5. Step 5: Solve for x
   x = 2,497,727.38/2,590.56
6. Step 6: Final answer
   x = 964.17