Finding the Fourth Proportional to 1,139.50, 1,572.66 and 673.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.50 : 1,572.66 = 673.78 : x
2. Step 2: Convert to fraction form
   1,139.50/1,572.66 = 673.78/x
3. Step 3: Cross multiply
   1,139.50x = 1,572.66 × 673.78
4. Step 4: Simplify right side
   1,139.50x = 1,059,626.85
5. Step 5: Solve for x
   x = 1,059,626.85/1,139.50
6. Step 6: Final answer
   x = 929.91