Finding the Fourth Proportional to 1,139.22, 1,572.15 and 641.88

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.22 : 1,572.15 = 641.88 : x
2. Step 2: Convert to fraction form
   1,139.22/1,572.15 = 641.88/x
3. Step 3: Cross multiply
   1,139.22x = 1,572.15 × 641.88
4. Step 4: Simplify right side
   1,139.22x = 1,009,131.64
5. Step 5: Solve for x
   x = 1,009,131.64/1,139.22
6. Step 6: Final answer
   x = 885.81