Finding the Fourth Proportional to 1,386.90, 1,913.91 and 789.47

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.90 : 1,913.91 = 789.47 : x
2. Step 2: Convert to fraction form
   1,386.90/1,913.91 = 789.47/x
3. Step 3: Cross multiply
   1,386.90x = 1,913.91 × 789.47
4. Step 4: Simplify right side
   1,386.90x = 1,510,964.96
5. Step 5: Solve for x
   x = 1,510,964.96/1,386.90
6. Step 6: Final answer
   x = 1,089.45