Finding the Fourth Proportional to 2,291.72, 3,436.78 and 905

Step by Step Solution

1. Step 1: Write the proportion equation
   2,291.72 : 3,436.78 = 905 : x
2. Step 2: Convert to fraction form
   2,291.72/3,436.78 = 905/x
3. Step 3: Cross multiply
   2,291.72x = 3,436.78 × 905
4. Step 4: Simplify right side
   2,291.72x = 3,110,285.90
5. Step 5: Solve for x
   x = 3,110,285.90/2,291.72
6. Step 6: Final answer
   x = 1,357.18