Finding the Fourth Proportional to 1,105.20, 1,654.56 and 861.90

Step by Step Solution

1. Step 1: Write the proportion equation
   1,105.20 : 1,654.56 = 861.90 : x
2. Step 2: Convert to fraction form
   1,105.20/1,654.56 = 861.90/x
3. Step 3: Cross multiply
   1,105.20x = 1,654.56 × 861.90
4. Step 4: Simplify right side
   1,105.20x = 1,426,065.26
5. Step 5: Solve for x
   x = 1,426,065.26/1,105.20
6. Step 6: Final answer
   x = 1,290.32