Finding the Fourth Proportional to 2,215.86, 3,057.57 and 1,221.15

Step by Step Solution

1. Step 1: Write the proportion equation
   2,215.86 : 3,057.57 = 1,221.15 : x
2. Step 2: Convert to fraction form
   2,215.86/3,057.57 = 1,221.15/x
3. Step 3: Cross multiply
   2,215.86x = 3,057.57 × 1,221.15
4. Step 4: Simplify right side
   2,215.86x = 3,733,751.61
5. Step 5: Solve for x
   x = 3,733,751.61/2,215.86
6. Step 6: Final answer
   x = 1,685.01