Finding the Fourth Proportional to 1,338.63, 2,005.20 and 789.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,338.63 : 2,005.20 = 789.15 : x
2. Step 2: Convert to fraction form
   1,338.63/2,005.20 = 789.15/x
3. Step 3: Cross multiply
   1,338.63x = 2,005.20 × 789.15
4. Step 4: Simplify right side
   1,338.63x = 1,582,403.58
5. Step 5: Solve for x
   x = 1,582,403.58/1,338.63
6. Step 6: Final answer
   x = 1,182.11