Finding the Fourth Proportional to 2,216.72, 3,059.20 and 1,221.99

Step by Step Solution

1. Step 1: Write the proportion equation
   2,216.72 : 3,059.20 = 1,221.99 : x
2. Step 2: Convert to fraction form
   2,216.72/3,059.20 = 1,221.99/x
3. Step 3: Cross multiply
   2,216.72x = 3,059.20 × 1,221.99
4. Step 4: Simplify right side
   2,216.72x = 3,738,310.47
5. Step 5: Solve for x
   x = 3,738,310.47/2,216.72
6. Step 6: Final answer
   x = 1,686.42