Finding the Fourth Proportional to 1,139.19, 1,571.94 and 641.83

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.19 : 1,571.94 = 641.83 : x
2. Step 2: Convert to fraction form
   1,139.19/1,571.94 = 641.83/x
3. Step 3: Cross multiply
   1,139.19x = 1,571.94 × 641.83
4. Step 4: Simplify right side
   1,139.19x = 1,008,914.32
5. Step 5: Solve for x
   x = 1,008,914.32/1,139.19
6. Step 6: Final answer
   x = 885.64