Finding the Fourth Proportional to 1,379.92, 1,904.12 and 820.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,379.92 : 1,904.12 = 820.40 : x
2. Step 2: Convert to fraction form
   1,379.92/1,904.12 = 820.40/x
3. Step 3: Cross multiply
   1,379.92x = 1,904.12 × 820.40
4. Step 4: Simplify right side
   1,379.92x = 1,562,140.05
5. Step 5: Solve for x
   x = 1,562,140.05/1,379.92
6. Step 6: Final answer
   x = 1,132.05