Finding the Fourth Proportional to 1,139.42, 1,572.46 and 642.14

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.42 : 1,572.46 = 642.14 : x
2. Step 2: Convert to fraction form
   1,139.42/1,572.46 = 642.14/x
3. Step 3: Cross multiply
   1,139.42x = 1,572.46 × 642.14
4. Step 4: Simplify right side
   1,139.42x = 1,009,739.46
5. Step 5: Solve for x
   x = 1,009,739.46/1,139.42
6. Step 6: Final answer
   x = 886.19