Finding the Fourth Proportional to 1,139.52, 1,572.48 and 642.16

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.52 : 1,572.48 = 642.16 : x
2. Step 2: Convert to fraction form
   1,139.52/1,572.48 = 642.16/x
3. Step 3: Cross multiply
   1,139.52x = 1,572.48 × 642.16
4. Step 4: Simplify right side
   1,139.52x = 1,009,783.76
5. Step 5: Solve for x
   x = 1,009,783.76/1,139.52
6. Step 6: Final answer
   x = 886.15