Finding the Fourth Proportional to 1,386.93, 1,914.12 and 789.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.93 : 1,914.12 = 789.57 : x
2. Step 2: Convert to fraction form
   1,386.93/1,914.12 = 789.57/x
3. Step 3: Cross multiply
   1,386.93x = 1,914.12 × 789.57
4. Step 4: Simplify right side
   1,386.93x = 1,511,331.73
5. Step 5: Solve for x
   x = 1,511,331.73/1,386.93
6. Step 6: Final answer
   x = 1,089.70