Finding the Fourth Proportional to 1,139.94, 1,573.13 and 642.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.94 : 1,573.13 = 642.55 : x
2. Step 2: Convert to fraction form
   1,139.94/1,573.13 = 642.55/x
3. Step 3: Cross multiply
   1,139.94x = 1,573.13 × 642.55
4. Step 4: Simplify right side
   1,139.94x = 1,010,814.68
5. Step 5: Solve for x
   x = 1,010,814.68/1,139.94
6. Step 6: Final answer
   x = 886.73