Finding the Fourth Proportional to 2,215.78, 3,057.61 and 1,221

Step by Step Solution

1. Step 1: Write the proportion equation
   2,215.78 : 3,057.61 = 1,221 : x
2. Step 2: Convert to fraction form
   2,215.78/3,057.61 = 1,221/x
3. Step 3: Cross multiply
   2,215.78x = 3,057.61 × 1,221
4. Step 4: Simplify right side
   2,215.78x = 3,733,341.81
5. Step 5: Solve for x
   x = 3,733,341.81/2,215.78
6. Step 6: Final answer
   x = 1,684.89