Finding the Fourth Proportional to 1,040.82, 1,436.57 and 642.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,040.82 : 1,436.57 = 642.57 : x
2. Step 2: Convert to fraction form
   1,040.82/1,436.57 = 642.57/x
3. Step 3: Cross multiply
   1,040.82x = 1,436.57 × 642.57
4. Step 4: Simplify right side
   1,040.82x = 923,096.78
5. Step 5: Solve for x
   x = 923,096.78/1,040.82
6. Step 6: Final answer
   x = 886.89