Finding the Fourth Proportional to 1,139.02, 1,571.90 and 641.71

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.02 : 1,571.90 = 641.71 : x
2. Step 2: Convert to fraction form
   1,139.02/1,571.90 = 641.71/x
3. Step 3: Cross multiply
   1,139.02x = 1,571.90 × 641.71
4. Step 4: Simplify right side
   1,139.02x = 1,008,696.81
5. Step 5: Solve for x
   x = 1,008,696.81/1,139.02
6. Step 6: Final answer
   x = 885.58