Finding the Fourth Proportional to 1,139.70, 1,572.59 and 660.98

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.70 : 1,572.59 = 660.98 : x
2. Step 2: Convert to fraction form
   1,139.70/1,572.59 = 660.98/x
3. Step 3: Cross multiply
   1,139.70x = 1,572.59 × 660.98
4. Step 4: Simplify right side
   1,139.70x = 1,039,456.12
5. Step 5: Solve for x
   x = 1,039,456.12/1,139.70
6. Step 6: Final answer
   x = 912.04