Finding the Fourth Proportional to 1,386.90, 1,913.60 and 789.32

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.90 : 1,913.60 = 789.32 : x
2. Step 2: Convert to fraction form
   1,386.90/1,913.60 = 789.32/x
3. Step 3: Cross multiply
   1,386.90x = 1,913.60 × 789.32
4. Step 4: Simplify right side
   1,386.90x = 1,510,429.24
5. Step 5: Solve for x
   x = 1,510,429.24/1,386.90
6. Step 6: Final answer
   x = 1,089.07