Finding the Fourth Proportional to 1,013.55, 1,398.54 and 640.62

Step by Step Solution

1. Step 1: Write the proportion equation
   1,013.55 : 1,398.54 = 640.62 : x
2. Step 2: Convert to fraction form
   1,013.55/1,398.54 = 640.62/x
3. Step 3: Cross multiply
   1,013.55x = 1,398.54 × 640.62
4. Step 4: Simplify right side
   1,013.55x = 895,932.69
5. Step 5: Solve for x
   x = 895,932.69/1,013.55
6. Step 6: Final answer
   x = 883.96