Finding the Fourth Proportional to 1,408.77, 1,939.23 and 1,221.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,408.77 : 1,939.23 = 1,221.15 : x
2. Step 2: Convert to fraction form
   1,408.77/1,939.23 = 1,221.15/x
3. Step 3: Cross multiply
   1,408.77x = 1,939.23 × 1,221.15
4. Step 4: Simplify right side
   1,408.77x = 2,368,090.71
5. Step 5: Solve for x
   x = 2,368,090.71/1,408.77
6. Step 6: Final answer
   x = 1,680.96