Finding the Fourth Proportional to 1,379.16, 1,903.20 and 789.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,379.16 : 1,903.20 = 789.72 : x
2. Step 2: Convert to fraction form
   1,379.16/1,903.20 = 789.72/x
3. Step 3: Cross multiply
   1,379.16x = 1,903.20 × 789.72
4. Step 4: Simplify right side
   1,379.16x = 1,502,995.10
5. Step 5: Solve for x
   x = 1,502,995.10/1,379.16
6. Step 6: Final answer
   x = 1,089.79