Finding the Fourth Proportional to 1,139.64, 1,572.69 and 642.27

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.64 : 1,572.69 = 642.27 : x
2. Step 2: Convert to fraction form
   1,139.64/1,572.69 = 642.27/x
3. Step 3: Cross multiply
   1,139.64x = 1,572.69 × 642.27
4. Step 4: Simplify right side
   1,139.64x = 1,010,091.61
5. Step 5: Solve for x
   x = 1,010,091.61/1,139.64
6. Step 6: Final answer
   x = 886.33