Finding the Fourth Proportional to 1,380.20, 1,904.10 and 855.86

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.20 : 1,904.10 = 855.86 : x
2. Step 2: Convert to fraction form
   1,380.20/1,904.10 = 855.86/x
3. Step 3: Cross multiply
   1,380.20x = 1,904.10 × 855.86
4. Step 4: Simplify right side
   1,380.20x = 1,629,643.03
5. Step 5: Solve for x
   x = 1,629,643.03/1,380.20
6. Step 6: Final answer
   x = 1,180.73