Finding the Fourth Proportional to 1,139.25, 1,572.21 and 641.86

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.25 : 1,572.21 = 641.86 : x
2. Step 2: Convert to fraction form
   1,139.25/1,572.21 = 641.86/x
3. Step 3: Cross multiply
   1,139.25x = 1,572.21 × 641.86
4. Step 4: Simplify right side
   1,139.25x = 1,009,141.41
5. Step 5: Solve for x
   x = 1,009,141.41/1,139.25
6. Step 6: Final answer
   x = 885.79