Finding the Fourth Proportional to 2,215.72, 3,057.77 and 1,221.07

Step by Step Solution

1. Step 1: Write the proportion equation
   2,215.72 : 3,057.77 = 1,221.07 : x
2. Step 2: Convert to fraction form
   2,215.72/3,057.77 = 1,221.07/x
3. Step 3: Cross multiply
   2,215.72x = 3,057.77 × 1,221.07
4. Step 4: Simplify right side
   2,215.72x = 3,733,745.11
5. Step 5: Solve for x
   x = 3,733,745.11/2,215.72
6. Step 6: Final answer
   x = 1,685.12