Finding the Fourth Proportional to 1,139.61, 1,572.68 and 642.27

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.61 : 1,572.68 = 642.27 : x
2. Step 2: Convert to fraction form
   1,139.61/1,572.68 = 642.27/x
3. Step 3: Cross multiply
   1,139.61x = 1,572.68 × 642.27
4. Step 4: Simplify right side
   1,139.61x = 1,010,085.18
5. Step 5: Solve for x
   x = 1,010,085.18/1,139.61
6. Step 6: Final answer
   x = 886.34