Finding the Fourth Proportional to 1,139.62, 1,571.89 and 720.51

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.62 : 1,571.89 = 720.51 : x
2. Step 2: Convert to fraction form
   1,139.62/1,571.89 = 720.51/x
3. Step 3: Cross multiply
   1,139.62x = 1,571.89 × 720.51
4. Step 4: Simplify right side
   1,139.62x = 1,132,562.46
5. Step 5: Solve for x
   x = 1,132,562.46/1,139.62
6. Step 6: Final answer
   x = 993.81