Finding the Fourth Proportional to 2,105.79, 2,905.71 and 1,221.47

Step by Step Solution

1. Step 1: Write the proportion equation
   2,105.79 : 2,905.71 = 1,221.47 : x
2. Step 2: Convert to fraction form
   2,105.79/2,905.71 = 1,221.47/x
3. Step 3: Cross multiply
   2,105.79x = 2,905.71 × 1,221.47
4. Step 4: Simplify right side
   2,105.79x = 3,549,223.07
5. Step 5: Solve for x
   x = 3,549,223.07/2,105.79
6. Step 6: Final answer
   x = 1,685.46