Finding the Fourth Proportional to 2,215.61, 3,057.55 and 1,220.90

Step by Step Solution

1. Step 1: Write the proportion equation
   2,215.61 : 3,057.55 = 1,220.90 : x
2. Step 2: Convert to fraction form
   2,215.61/3,057.55 = 1,220.90/x
3. Step 3: Cross multiply
   2,215.61x = 3,057.55 × 1,220.90
4. Step 4: Simplify right side
   2,215.61x = 3,732,967.39
5. Step 5: Solve for x
   x = 3,732,967.39/2,215.61
6. Step 6: Final answer
   x = 1,684.85