Finding the Fourth Proportional to 1,387.30, 1,914.29 and 789.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.30 : 1,914.29 = 789.78 : x
2. Step 2: Convert to fraction form
   1,387.30/1,914.29 = 789.78/x
3. Step 3: Cross multiply
   1,387.30x = 1,914.29 × 789.78
4. Step 4: Simplify right side
   1,387.30x = 1,511,867.96
5. Step 5: Solve for x
   x = 1,511,867.96/1,387.30
6. Step 6: Final answer
   x = 1,089.79