Finding the Fourth Proportional to 1,378.86, 1,902.86 and 789.58

Step by Step Solution

1. Step 1: Write the proportion equation
   1,378.86 : 1,902.86 = 789.58 : x
2. Step 2: Convert to fraction form
   1,378.86/1,902.86 = 789.58/x
3. Step 3: Cross multiply
   1,378.86x = 1,902.86 × 789.58
4. Step 4: Simplify right side
   1,378.86x = 1,502,460.20
5. Step 5: Solve for x
   x = 1,502,460.20/1,378.86
6. Step 6: Final answer
   x = 1,089.64