Finding the Fourth Proportional to 1,118.19, 1,678.17 and 789.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,118.19 : 1,678.17 = 789.78 : x
2. Step 2: Convert to fraction form
   1,118.19/1,678.17 = 789.78/x
3. Step 3: Cross multiply
   1,118.19x = 1,678.17 × 789.78
4. Step 4: Simplify right side
   1,118.19x = 1,325,385.10
5. Step 5: Solve for x
   x = 1,325,385.10/1,118.19
6. Step 6: Final answer
   x = 1,185.30