Finding the Fourth Proportional to 2,105.71, 2,905.91 and 1,221.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.71 : 2,905.91 = 1,221.78 : x
2. Step 2: Convert to fraction form
   2,105.71/2,905.91 = 1,221.78/x
3. Step 3: Cross multiply
   2,105.71x = 2,905.91 × 1,221.78
4. Step 4: Simplify right side
   2,105.71x = 3,550,382.72
5. Step 5: Solve for x
   x = 3,550,382.72/2,105.71
6. Step 6: Final answer
   x = 1,686.07