Finding the Fourth Proportional to 1,139.97, 1,573.05 and 642.69

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.97 : 1,573.05 = 642.69 : x
2. Step 2: Convert to fraction form
   1,139.97/1,573.05 = 642.69/x
3. Step 3: Cross multiply
   1,139.97x = 1,573.05 × 642.69
4. Step 4: Simplify right side
   1,139.97x = 1,010,985.91
5. Step 5: Solve for x
   x = 1,010,985.91/1,139.97
6. Step 6: Final answer
   x = 886.85