Finding the Fourth Proportional to 1,138.57, 1,571.32 and 641.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,138.57 : 1,571.32 = 641.30 : x
2. Step 2: Convert to fraction form
   1,138.57/1,571.32 = 641.30/x
3. Step 3: Cross multiply
   1,138.57x = 1,571.32 × 641.30
4. Step 4: Simplify right side
   1,138.57x = 1,007,693.72
5. Step 5: Solve for x
   x = 1,007,693.72/1,138.57
6. Step 6: Final answer
   x = 885.05