Finding the Fourth Proportional to 2,105.64, 2,905.72 and 1,221.39

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.64 : 2,905.72 = 1,221.39 : x
2. Step 2: Convert to fraction form
   2,105.64/2,905.72 = 1,221.39/x
3. Step 3: Cross multiply
   2,105.64x = 2,905.72 × 1,221.39
4. Step 4: Simplify right side
   2,105.64x = 3,549,017.35
5. Step 5: Solve for x
   x = 3,549,017.35/2,105.64
6. Step 6: Final answer
   x = 1,685.48