Finding the Fourth Proportional to 1,139.58, 1,572.63 and 642.24

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.58 : 1,572.63 = 642.24 : x
2. Step 2: Convert to fraction form
   1,139.58/1,572.63 = 642.24/x
3. Step 3: Cross multiply
   1,139.58x = 1,572.63 × 642.24
4. Step 4: Simplify right side
   1,139.58x = 1,010,005.89
5. Step 5: Solve for x
   x = 1,010,005.89/1,139.58
6. Step 6: Final answer
   x = 886.30