Finding the Fourth Proportional to 1,139.05, 1,572.06 and 641.73

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.05 : 1,572.06 = 641.73 : x
2. Step 2: Convert to fraction form
   1,139.05/1,572.06 = 641.73/x
3. Step 3: Cross multiply
   1,139.05x = 1,572.06 × 641.73
4. Step 4: Simplify right side
   1,139.05x = 1,008,838.06
5. Step 5: Solve for x
   x = 1,008,838.06/1,139.05
6. Step 6: Final answer
   x = 885.68