Finding the Fourth Proportional to 1,137.05, 1,569.20 and 639.71

Step by Step Solution

1. Step 1: Write the proportion equation
   1,137.05 : 1,569.20 = 639.71 : x
2. Step 2: Convert to fraction form
   1,137.05/1,569.20 = 639.71/x
3. Step 3: Cross multiply
   1,137.05x = 1,569.20 × 639.71
4. Step 4: Simplify right side
   1,137.05x = 1,003,821.89
5. Step 5: Solve for x
   x = 1,003,821.89/1,137.05
6. Step 6: Final answer
   x = 882.83