Finding the Fourth Proportional to 1,013.63, 1,398.71 and 640.47

Step by Step Solution

1. Step 1: Write the proportion equation
   1,013.63 : 1,398.71 = 640.47 : x
2. Step 2: Convert to fraction form
   1,013.63/1,398.71 = 640.47/x
3. Step 3: Cross multiply
   1,013.63x = 1,398.71 × 640.47
4. Step 4: Simplify right side
   1,013.63x = 895,828.59
5. Step 5: Solve for x
   x = 895,828.59/1,013.63
6. Step 6: Final answer
   x = 883.79