Finding the Fourth Proportional to 2,105.78, 2,905.74 and 1,221.44

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.78 : 2,905.74 = 1,221.44 : x
2. Step 2: Convert to fraction form
   2,105.78/2,905.74 = 1,221.44/x
3. Step 3: Cross multiply
   2,105.78x = 2,905.74 × 1,221.44
4. Step 4: Simplify right side
   2,105.78x = 3,549,172.54
5. Step 5: Solve for x
   x = 3,549,172.54/2,105.78
6. Step 6: Final answer
   x = 1,685.45