Finding the Fourth Proportional to 1,139.82, 1,572.93 and 642.62

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.82 : 1,572.93 = 642.62 : x
2. Step 2: Convert to fraction form
   1,139.82/1,572.93 = 642.62/x
3. Step 3: Cross multiply
   1,139.82x = 1,572.93 × 642.62
4. Step 4: Simplify right side
   1,139.82x = 1,010,790.02
5. Step 5: Solve for x
   x = 1,010,790.02/1,139.82
6. Step 6: Final answer
   x = 886.80