Finding the Fourth Proportional to 1,387.16, 1,914.15 and 789.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.16 : 1,914.15 = 789.61 : x
2. Step 2: Convert to fraction form
   1,387.16/1,914.15 = 789.61/x
3. Step 3: Cross multiply
   1,387.16x = 1,914.15 × 789.61
4. Step 4: Simplify right side
   1,387.16x = 1,511,431.98
5. Step 5: Solve for x
   x = 1,511,431.98/1,387.16
6. Step 6: Final answer
   x = 1,089.59