Finding the Fourth Proportional to 2,105.29, 2,905.47 and 1,221.40

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.29 : 2,905.47 = 1,221.40 : x
2. Step 2: Convert to fraction form
   2,105.29/2,905.47 = 1,221.40/x
3. Step 3: Cross multiply
   2,105.29x = 2,905.47 × 1,221.40
4. Step 4: Simplify right side
   2,105.29x = 3,548,741.06
5. Step 5: Solve for x
   x = 3,548,741.06/2,105.29
6. Step 6: Final answer
   x = 1,685.63