Finding the Fourth Proportional to 2,178.21, 3,005.97 and 1,221.15

Step by Step Solution

1. Step 1: Write the proportion equation
   2,178.21 : 3,005.97 = 1,221.15 : x
2. Step 2: Convert to fraction form
   2,178.21/3,005.97 = 1,221.15/x
3. Step 3: Cross multiply
   2,178.21x = 3,005.97 × 1,221.15
4. Step 4: Simplify right side
   2,178.21x = 3,670,740.27
5. Step 5: Solve for x
   x = 3,670,740.27/2,178.21
6. Step 6: Final answer
   x = 1,685.21