Finding the Fourth Proportional to 2,105.91, 2,905.90 and 1,221.59

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.91 : 2,905.90 = 1,221.59 : x
2. Step 2: Convert to fraction form
   2,105.91/2,905.90 = 1,221.59/x
3. Step 3: Cross multiply
   2,105.91x = 2,905.90 × 1,221.59
4. Step 4: Simplify right side
   2,105.91x = 3,549,818.38
5. Step 5: Solve for x
   x = 3,549,818.38/2,105.91
6. Step 6: Final answer
   x = 1,685.65