Finding the Fourth Proportional to 1,139.59, 1,572.78 and 789.67

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.59 : 1,572.78 = 789.67 : x
2. Step 2: Convert to fraction form
   1,139.59/1,572.78 = 789.67/x
3. Step 3: Cross multiply
   1,139.59x = 1,572.78 × 789.67
4. Step 4: Simplify right side
   1,139.59x = 1,241,977.18
5. Step 5: Solve for x
   x = 1,241,977.18/1,139.59
6. Step 6: Final answer
   x = 1,089.85