Finding the Fourth Proportional to 2,105.73, 2,905.90 and 1,221.57

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.73 : 2,905.90 = 1,221.57 : x
2. Step 2: Convert to fraction form
   2,105.73/2,905.90 = 1,221.57/x
3. Step 3: Cross multiply
   2,105.73x = 2,905.90 × 1,221.57
4. Step 4: Simplify right side
   2,105.73x = 3,549,757.21
5. Step 5: Solve for x
   x = 3,549,757.21/2,105.73
6. Step 6: Final answer
   x = 1,685.76