Finding the Fourth Proportional to 1,091.10, 1,505.31 and 855.96

Step by Step Solution

1. Step 1: Write the proportion equation
   1,091.10 : 1,505.31 = 855.96 : x
2. Step 2: Convert to fraction form
   1,091.10/1,505.31 = 855.96/x
3. Step 3: Cross multiply
   1,091.10x = 1,505.31 × 855.96
4. Step 4: Simplify right side
   1,091.10x = 1,288,485.15
5. Step 5: Solve for x
   x = 1,288,485.15/1,091.10
6. Step 6: Final answer
   x = 1,180.90