Finding the Fourth Proportional to 2,661.33, 3,990.69 and 811.95

Step by Step Solution

1. Step 1: Write the proportion equation
   2,661.33 : 3,990.69 = 811.95 : x
2. Step 2: Convert to fraction form
   2,661.33/3,990.69 = 811.95/x
3. Step 3: Cross multiply
   2,661.33x = 3,990.69 × 811.95
4. Step 4: Simplify right side
   2,661.33x = 3,240,240.75
5. Step 5: Solve for x
   x = 3,240,240.75/2,661.33
6. Step 6: Final answer
   x = 1,217.53