Finding the Fourth Proportional to 1,091.90, 1,638.15 and 443.09

Step by Step Solution

1. Step 1: Write the proportion equation
   1,091.90 : 1,638.15 = 443.09 : x
2. Step 2: Convert to fraction form
   1,091.90/1,638.15 = 443.09/x
3. Step 3: Cross multiply
   1,091.90x = 1,638.15 × 443.09
4. Step 4: Simplify right side
   1,091.90x = 725,847.88
5. Step 5: Solve for x
   x = 725,847.88/1,091.90
6. Step 6: Final answer
   x = 664.76