Finding the Fourth Proportional to 1,137.98, 1,570.31 and 640.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,137.98 : 1,570.31 = 640.55 : x
2. Step 2: Convert to fraction form
   1,137.98/1,570.31 = 640.55/x
3. Step 3: Cross multiply
   1,137.98x = 1,570.31 × 640.55
4. Step 4: Simplify right side
   1,137.98x = 1,005,862.58
5. Step 5: Solve for x
   x = 1,005,862.58/1,137.98
6. Step 6: Final answer
   x = 883.90