Finding the Fourth Proportional to 1,139.94, 1,573.16 and 642.67

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.94 : 1,573.16 = 642.67 : x
2. Step 2: Convert to fraction form
   1,139.94/1,573.16 = 642.67/x
3. Step 3: Cross multiply
   1,139.94x = 1,573.16 × 642.67
4. Step 4: Simplify right side
   1,139.94x = 1,011,015.59
5. Step 5: Solve for x
   x = 1,011,015.59/1,139.94
6. Step 6: Final answer
   x = 886.90