Finding the Fourth Proportional to 1,920.72, 2,650.42 and 1,221.84

Step by Step Solution

1. Step 1: Write the proportion equation
   1,920.72 : 2,650.42 = 1,221.84 : x
2. Step 2: Convert to fraction form
   1,920.72/2,650.42 = 1,221.84/x
3. Step 3: Cross multiply
   1,920.72x = 2,650.42 × 1,221.84
4. Step 4: Simplify right side
   1,920.72x = 3,238,389.17
5. Step 5: Solve for x
   x = 3,238,389.17/1,920.72
6. Step 6: Final answer
   x = 1,686.03