Finding the Fourth Proportional to 2,215.87, 3,057.85 and 1,221.12

Step by Step Solution

1. Step 1: Write the proportion equation
   2,215.87 : 3,057.85 = 1,221.12 : x
2. Step 2: Convert to fraction form
   2,215.87/3,057.85 = 1,221.12/x
3. Step 3: Cross multiply
   2,215.87x = 3,057.85 × 1,221.12
4. Step 4: Simplify right side
   2,215.87x = 3,734,003.32
5. Step 5: Solve for x
   x = 3,734,003.32/2,215.87
6. Step 6: Final answer
   x = 1,685.12