Finding the Fourth Proportional to 1,287.69, 1,777.41 and 791.05

Step by Step Solution

1. Step 1: Write the proportion equation
   1,287.69 : 1,777.41 = 791.05 : x
2. Step 2: Convert to fraction form
   1,287.69/1,777.41 = 791.05/x
3. Step 3: Cross multiply
   1,287.69x = 1,777.41 × 791.05
4. Step 4: Simplify right side
   1,287.69x = 1,406,020.18
5. Step 5: Solve for x
   x = 1,406,020.18/1,287.69
6. Step 6: Final answer
   x = 1,091.89