Finding the Fourth Proportional to 1,013.94, 1,399.25 and 640.53

Step by Step Solution

1. Step 1: Write the proportion equation
   1,013.94 : 1,399.25 = 640.53 : x
2. Step 2: Convert to fraction form
   1,013.94/1,399.25 = 640.53/x
3. Step 3: Cross multiply
   1,013.94x = 1,399.25 × 640.53
4. Step 4: Simplify right side
   1,013.94x = 896,263.20
5. Step 5: Solve for x
   x = 896,263.20/1,013.94
6. Step 6: Final answer
   x = 883.94